


Maximum Enthalpy

by Allamarain



Category: Doctor Who (2005)
Genre: Action/Adventure, Gen, Giant Bugs, I know just enough physics to BS this, Meeting Past Doctors, Minor Character Death, Timey-Wimey
Language: English
Status: Completed
Published: 2020-05-26
Updated: 2020-07-08
Packaged: 2021-03-02 17:01:54
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 6
Words: 23,340
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24380245
Author URL: https://archiveofourown.org/users/Allamarain/pseuds/Allamarain
Summary: Damaged in mid-flight, The TARDIS is stuck on an unfamiliar, barren planet.  When the Doctor and fam head off to look for help, they must face hostile locals and oversized insects.But nothing will prepare them for the greatest challenge of all: the Doctor reverting to her past selves.Set between Series 11 and 12
Relationships: Thirteenth Doctor & Yasmin Khan & Graham O'Brien & Ryan Sinclair
Comments: 31
Kudos: 132





	1. Chapter 1

When Ryan opened his eyes, and it was pitch black, and the stench of smoke filled the air. 

He was laying on his side, aching from being thrown to the ground. He gave his limbs a tentative wriggle. Nothing serious, maybe a few bruises. One moment, they'd been in the TARDIS, on their way back to Sheffield. The next, the TARDIS was being whipped around so quickly he'd been thrown off the stairs. He lost track of everything he'd crashed into after the lights went out. He might have lost consciousness for a moment; he wasn't sure. All he knew now was he was aching and sore, and he didn't know what happened.

A loud bell sounded from somewhere overhead, with slow, regular gongs. His stomach tightened as he realized he had no idea where he was. He grasped around but caught nothing but empty air. 

"Fam? Is everyone all right?" The Doctor's voice, somewhere in the dark, shouting over the bell. He relaxed, but only a smidge. At least if the Doctor was around, he wasn't alone.

He heard a groan coming from nearby. "Yaz, you okay?" he asked.

"I'm all right," she sounded weary. "Where are we? Did we get thrown off the TARDIS?"

"No, still aboard, but she's sustained major damage." The Doctor's voice was high pitched and tight like she was trying to keep from panicking. "The power's gone out."

"Yeah, I can see that, Doc. Or rather, I can't." Graham, from across the room. "Haven't had a ride like that since the roller coasters at Adventure Island. What happened?"

"I don't know." 

"Where are we?"

"Haven't the foggiest."

To Ryan, that they were still aboard the TARDIS was something of a relief. But he'd never seen the lights completely out in the console room, or for that matter, anywhere else. And the hum, the ever-present hum that he could feel through the soles of his shoes, was gone. He reached down to touch the grating, and it was still. Between that and the smoke, he had a feeling the situation was much more serious than the Doctor was letting on. 

The Doctor pulled herself up by the edge of the console. "I'm going down to the engine room. Wait here," she announced, trying to keep her voice steady. The telepathic link of the TARDIS, normally a comforting presence in the back of her mind, had been reduced to was a faint pulse. She had no idea what could have caused this to happen. There'd been no obstacles in her way, no weapons. Very few things could damage a TARDIS like this. She wasn't even certain it could be fixed. But before she could do anything, she needed to assess the damage. She walked out of the console room, arms in front of her to keep from bumping into anything. 

Ryan scooted over until his hands came up against one of the crystal pillars, and pulled himself up. Nothing was broken, though his arm was sore. Now if only he could see. Then it occurred to him: he could use his phone. He must have hit his head, if he'd forgotten that. Scanning the console room using flashlight mode, he found Yaz a few feet away, sprawled on the floor. "Yaz, can you get up?"

She winced slightly as she stood. "I should be fine. Been through worse in PE." The only thing she'd been popular for in secondary was as a target in dodgeball, and the teachers had done nothing to stop her tormentors. 

"Let's check on Graham." Holding the edge of the console, he walked around until the flashlight showed his grandfather's form. 

"I'm fine. Takes a little more than being banged around the TARDIS to stop me." He tried to smile, but even in the darkness, Ryan could sense the concern. 

They chatted a little as they waited for the Doctor to return. "Surprised this hasn't happened to us before. The Doc said it was an old ship, and she's always doing repairs of some sort," Graham said.

"It's never been this bad though. What if she can't fix it?" Yaz rubbed the back of her head. "We could be stuck here."

"We don't even know where here is," Ryan said. "I'm gonna check." Maybe they were on Earth and could go home while the Doctor made repairs. Something told him that was unlikely to be the case.

"She said to wait here." Yaz reminded him.

"I'm just going to look out the doors." Carefully stepping over a bundle of wires, he made his way to the front doors. Outside was completely black. "Can't see a thing." Returning to his friends, he squatted on the ground, careful to avoid touching anything. 

"The Doc will sort all this out, don't worry," Graham said. "She's never let us down before."

"Yeah, I know," he replied, not entirely convinced. What happened when the Doctor met a problem even she couldn't solve?

—  
An hour later, there was a soft whir, and lights spread through the console. The central pillar lit, though dimly. Ryan felt a flicker of hope. If the TARDIS was lit, they weren't stranded. 

"Good! It worked!" The Doctor appeared in the doorway. The faint glow from the central pillar reflected on her face. "Had to haul the backup generator out of storage, make a few adjustments-Ryan, I had to take apart your PlayStation."

He groaned despite the severity. It was his personal video game system, and he'd saved up to buy it. He reminded himself there were more pressing matters at hand.

The Doctor continued, "I was able to route all auxiliary power to the console, and at least see where we are." She rushed over to the console, bending over. Beads of sweat collected on her forehead as her brows furrowed. Ryan wasn't sure what she was seeing, but he'd been traveling with her long enough to know he didn't like the look of it. She staring in silence for a few moments, unmoving. 

"What is it, Doc?" Graham broke the tense silence.

"These readings. They're all nonsense. Never seen anything like it." She pointed to the screen as if he could decipher Gallifreyan text. She had no idea what was wrong with the TARDIS, and that was unusual. Over thousands of years, she'd encountered every problem known to the Type 40, and a few that weren't. What was happening now absolutely mystified her. 

"Did the console break in the crash?" Yaz ventured. 

"Possible. But either way, I don't know where we are or what's happened. The backup generator will run the console, but it's not enough power for her to take off."

The humans exchanged glances. "There must be something we can do, right? We can't just be stranded here," Yaz said.

"I'll get us out of here." Probably, the Doctor added to herself. She didn't want to worry the fam any more than they already were. "Let's see where we are the old fashioned way. I'll take a nip out and check." She strode out the door, coat swishing behind her.

The moment the Doctor stepped outside the TARDIS, she felt _wrong_.

A buzzing filled her head, making it hard to think. Her skin felt like it was crawling with millions of tiny insects. Out of instinct, she batted away at her arms before realizing nothing was there. Very strange. Something in the air, a poison perhaps? She stood, eyes scrunched shut in concentration. Was something trying to communicate with her? The buzzing continued but decreased to a low hum at the base of her skull. 

The air was cold, and she hugged herself as she took a few steps around the TARDIS. She probably shouldn't have simply walked out of her ship without protective shielding, or at least an umbrella. She was getting careless in her old age. Above her, the sky was dark, with only a few distant points of light appearing. She couldn't recognize any of the constellations. She didn't recognize the planet they were on either. Squatting down, she traced her finger along the ground. Perhaps a taste of dirt would tell her where she was. However, the ground was frozen solid. The only feature of the otherwise empty landscape was the silhouette of a massive, squat building, half a click ahead. Not too promising, but the only option she could see. 

Her fingers were beginning to stiffen, and she realized she was getting cold. It happened so infrequently, she'd forgotten the sensation. If she stayed out here much longer, she'd freeze like a popsicle. 

She went back inside to her friends. The buzzing and crawling she'd felt earlier had stopped once the making it easier to think. "Saw a big grey building before us. Love a big grey building. Actually, I don't, but we can go inside and maybe get some answers as to where we are. One thing though, it's a bit cold out there. Maybe 100 Kelvin? Best to put on some environmental suits. They're downstairs in the wardrobe." 

The fam nodded in agreement as they followed her out of the console room. She'd need an environmental suit for herself, too. Although the Doctor could withstand the temperature for a few minutes, she'd never survive the walk to the building. A part of her hated to leave the wounded ship alone, but they had no chance to survive if they didn't go out looking for solutions.

In the wardrobe, the Doctor pulled out four bright orange suits. Graham held one up to himself. The fabric was thin, almost flimsy. Black gloves, with short thin fingers, were attached at the end of each arm. "Are these like, astronaut suits?" He tried not to feel apprehensive. Despite the regular dangers they faced, the thought of wearing something that felt like a Halloween costume was more than a bit unnerving. 

"Yes, but much more advanced." Her coat bunched around her waist as she stepped into it. "Flexible, lightweight material, but incredibly strong. We'll need helmets and oxygen tanks too. There's oxygen in the atmosphere, but at these temperatures, breathing it would damage your lungs." Zipping up her suit, she rooted around in a box that was about half as high as she was. "They're around here somewhere." 

The addition of an oxygen tank only furthered Graham's apprehension. For a moment, he considered asking to stay with the TARDIS. Maybe someone would come along and offer to help. But he saw Ryan suiting up and eagerly asking Yaz if he made a good astronaut. He sighed. If Ryan wasn't afraid, he wouldn't be either, and someone had to be there to keep the lad out of trouble. Putting on the suit, he found it was at least comfortable, and the gloves stretched to perfectly fit his hands. He noticed tiny metal clips at the wrists. The gloves were removable, he noted. He just hoped the clips stayed in place while they were outside.

"Found everything! I'll give you each a hand! The oxygen tanks can be a little difficult to get used to." The Doctor sprung up with a handful of clear plastic helmets and other gadgets. It had taken her a while to find them. Graham wondered idly if the boxes in the wardrobe were also bigger on the inside. Every day with the Doctor, something surprised him. She helped him put on the oxygen tank and secure it to the suit attachment. At least th tanks were smaller and lighter than he expected. Wearing one felt no heavier than a backpack. 

Yaz gave them a quizzical look. "Doctor, will this be enough air?"

"We should be fine for at least six hours," she said. "Let's go."

—

As the Doctor set off from the TARDIS with her friends, things were happening near her ship.

The TARDIS was cleverly disguised as an Earth police box, but that was all it was; a disguise. Beneath the illusion lay a complex network of the fuselage, circuitry, shielding, and other parts of a space and time ship. Most of these are not important to our tale, except for one: exhaust.  
The TARDIS, like any other mode of transportation, requires a source of power. At the heart of the TARDIS lies the Eye of Harmony. The Eye of Harmony is responsible for creating artron energy, which is dispelled into the Time Vortex. But that was hardly the only thing dispelled. Notably, Hawking radiation from the Eye of Harmony's event horizon was collected by the Eye and vented through the exhaust ports. 

To most living creatures, this was harmless. For a select few, it was a boon.

Black bugs, no larger than a thumbnail, crawled mindlessly around the frozen ground, in search of a few scraps of ever-dwindling food. What they found was so much greater. The insects had survived the cold and near starvation, leaving them one of the few remaining life forms on this planet. They spent most of their time buried under the ground in search of warmth, chewing dirt in a near futile attempt to gather nutrients.  
Bathed by Hawking radiation, the bugs began to grow, doubling, tripling, then larger by orders of magnitude. They were strong and relentless. And they were so very, very hungry. 

—  
Despite the heavily locked entrance to the building, the Doctor was easily able to sonic it open. Inside was a vacant guard station, lined with thick glass and thicker stone. 

The Doctor pulled off her helmet first. "Temperature about 18 degrees. Should be fine." She motioned for the others to do the same, setting the helmets gently on the ground. She tried to avoid the slight tremor in her hands. The crawling and buzzing had returned as she stepped out of the TARDIS again. That ruled out something in the air, at least. Perhaps she was allergic to something on this planet. She wondered if she still had any celery back in the kitchen; it might come in handy. 

"Janus Point Base." Ryan read the inscription above the guard station. The place was eerily quiet, and it made him uneasy. "Seems like a military base of some sort, but there's no one here. Ever hear of it?"

"Never heard of it," The Doctor said. She ran her fingers along the walls, sonicing in a few places. "The walls are made of structural steel. It's practically brand new. No pitting, no corrosion, no crazing."

"Who'd build a brand new base and just abandon it?" asked Graham.

"Is an excellent question! Five points to Graham!" the Doctor pointed at him with glee. Graham gave her a smug smile. He didn't know what the current point totals were, and he expected the Doctor didn't know either, but he was happy to get some recognition. 

"What if it's not abandoned? What if the troops are comin'?" Ryan said. 

"Certainly possible. But in the meantime, let's have a look around." On either side of the guard station, there was a lengthy corridor, punctuated by evenly spaced overhead lights. "Graham and Yaz, go that way. Ryan, you're with me."

The corridor was lined with the same brushed steel as the entrance. They stopped in a few rooms; a mess area, a set of bunks, a shower. Nothing out of the ordinary. Meanwhile, the buzzing in her head was getting worse with every step. "Ryan, how are you feeling? We had a rough landing." She tried to sound casual, not wanting him to know what was happening to her, but if the fam was affected, she needed to know. 

"Feeling all right. A little achy." He rubbed his elbow through the environmental suit. Most of the other aches had subsided on the walk to the base."You?"

"Peachy keen. No worries." She gave him a small, tight smile, that suggested otherwise. As if she was eager for a quick subject change, she pulled him towards a door marked Laboratory. "Let's check out this room. Looks promising."

Inside was a mess, with glassware and small tubes covering every surface. "Someone's been here after all," Ryan said. He peered into an empty glass box, studying the readings below. He couldn't make out any of the symbols. "What's this?"

The Doctor leaned over. "Radioactive oxygen." At his startled look, she added, "It's shielded, you're fine as long as you…"

"Don't touch anything, I know." He held up his hands. 

She squinted. "Doesn't look like there's much left, anyway. It's not a very stable isotope." She walked around the lab, tracing her black-gloved fingers over the abandoned experiments. She leaned against the counter, touching her forehead. The crawling feeling was getting worse, and she wanted to jump out of her skin. 

Ryan felt a buzz in his jeans pocket. "Hold on." He unzipped his environmental suit to grab his phone-Yaz. He put it on speaker so they could both hear. 

"You need to come quick." Yaz was panicked on the other end of the line. "Graham and I found a body." 

"What kind of body?" The Doctor sprung to attention, forgetting her unease. 

"Human, I guess? I can't tell what killed them." She sounded on the verge of tears. 

"Stay put. I'll be right there." The Doctor ordered. She hoped whatever was giving her the crawlies wasn't lethal. To Ryan, she said, "Keep looking around, see if you can find out what experiments they were doing. I'll be back as soon as I can."

As she ran down the corridor, the crawling feeling grew to a crescendo. She found herself stopping, leaning against the wall. _I can't stop now, I need to check on Yaz and Graham. Keep them out of danger_. She willed herself to move, but her legs would not obey. Her stomach filled with nausea. 

Tiny sharp bursts of pain filled her fingertips. Gingerly, she pulled off the gloves of her environmental suit, to find a purple light emitting from them. She was dying. She must be. Something in this place must be killing her. She sank to the ground on hands and knees, wracked with pain. Breath came out in choked gasps. She needed to keep going. She had to rescue her friends. Get them home in one piece. She crawled along the ground, only making it a few meters before collapsing.  
The purple spread from her fingers, down her arms, covering her whole body. She only barely managed not to scream as white-hot pain shot through her entire pain.

Then a moment later, everything stopped. The crawling feeling dialed down to nearly zero, stuck in the background like supermarket music. The Doctor slowly got up. Taller, now. She must have regenerated, although it felt different this time. Was she a man again? Didn't matter; that could be sorted out later. What was important was saving the fam. The Doctor started running down the corridor again, only to run smack into the wall. _Right, new body, not very good at going straight ahead yet_. After a moment, the Doctor recovered and ran towards her friends. 

—  
Captain Trawker watched the strangers on the screens that lined the command center. These four didn't look like the typical intruders. He could sense a bit of desperation, but they were well equipped, and not even a hint of hunger among them. Not that they would like what they'd found. He paid particular attention to the one they called the Doctor; she seemed to be the leader among them. 

The command center was designed for at least ten people, but he'd longed designated it as his private sanctuary. He could see and hear everything that happened at the base. He didn't know what kind of weapons this group was carrying, and it was best not to find out personally. Trawker was a slight man, a mop of golden brown curls giving him a boyish appearance. In his own mind, he made up for it by being clever, much more clever than the half-wit brutes that made up his remaining squadron. It surprised nobody but him he'd been named base captain, back when such things still mattered. 

He tapped his comm. "Zone B. Intruders." He'd never been a man of many words. He sat back and waited to see what the intruders would do next.

—  
Graham avoided looking at the corpse in the center of the room. No matter how many dead bodies they saw, he could never get used to looking at them. The image of the man's face, his mouth in an O of shock, was burned into his mind. He shifted his weight. "Doc should have been here by now. What's keeping her?"

"Hope whatever got him didn't get her," Yaz said. She paced the length of the room where they'd found the body; it appeared to be a storage area of some sort. She tried to focus on the boxes, looking at the writing-the Doctor was always telling them to keep their eyes open and look for clues-but none of it registered. "But she's good at defending herself."

Graham nodded, not assured by this. "Maybe I should go look for her."

"She said to stay put."

"She says a lot of things. Don't properly look out for herself." He leaned against the wall. Every minute that passed made him more apprehensive. At the sound of footsteps, he felt a moment of relief, until he realized the footsteps sounded wrong. Heavier. Longer. He tensed his muscles, ready for a fight. 

"Here I am! Oooh, I'm Scottish again! Something sort of familiar about it though. Can't quite place it." A tall figure burst into the room, and Graham's mouth dropped.

The strange man before them was wearing the Doctor's orange environmental suit. He was an older man with rugged features, the most prominent of which was his incredibly large eyebrows. He looked at them with a wild-eyed grin, as if he expected they'd be glad to see him. His surprise turned into outrage. How dare he come in here like that! What had happened to her? Why was he wearing her suit? He and Yaz needed to find out what happened to the Doctor, fast. 

"Now, I'm sure you have a lot of questions…" the strange man began.

"Just one." Graham's eyes narrowed, his hands curled into fists. "What have you done to the Doctor?"


	2. Chapter 2

The stranger spread out his arms in a gesture of welcome. "It's me! I'm the Doctor!"

"I don't know who you are, but you ain't the Doc." Graham put up his hands in front of him, signaling the strange not to come any closer. He didn't know who this bloke was, and didn't like him claiming to be his friend. 

"No, no, no, it's definitely me. Look, see, I'm wearing the same outfit." He unzipped his environmental suit to reveal a tightly stretched rainbow shirt across the top half of his chest.   
He stared down in disgust. "Ugh. Rainbows. Dreadful. Not to mention this whole getup is unflattering. You two, forget you saw that." He hastily pulled up the zipper.

Graham stared in disbelief. "You're wearing her clothes too? What are you, some kind of pervert?!"

"No, it's me! I'm just in another body. Look, I know you." He gestured at Graham. "You were born and raised in Essex. As a boy, you skipped Sunday school to go fishing. You always carry a sandwich in your jacket in case we don't get to eat. You love West Ham United. In retrospect, it's probably because of the ham."

Graham didn't know how the stranger knew these things, but there were all sorts of strange aliens out there, aliens that could read minds wasn't much of a stretch. Out of the corner of his eye, he spotted a length of pipe. He grabbed it, not taking his attention off the man. "I can throw a mean swing with this. "

The man's expression darkened. "I've told you how much I hate weapons, Bill." 

Graham tightened his grip on the pipe. _Bill?_ "Don't know who you think I am, but I ain't Bill."

"Oh, right." The Doctor shook his head. No, this wasn't Bill. Bill was young and bright and asked so many questions that most of his friends didn't even think about and she...he couldn't think about what happened to her. He'd get mired in it. Best to focus on the now. "Regeneration sickness. At least I think that's what this is. Names, words, things get mixed up. Sometimes limbs." 

"Wait, regeneration?" Graham's voice softened slightly. A memory flickered into focus. The Doctor, in an oversized man's suit, describing it. _My whole body changed. Every cell in my body burning. Some of them are still at it now. Reordering, regenerating._ "You mentioned it. Before."

The man-the Doctor?-smiled. "Now you're catching up."

"But you look so different." Yaz studied him. She'd been watching everything in silence, taking it in. Everything about the Doctor was different from the person she'd gotten to know. She still wasn't entirely sure she believed it. "How do you choose?"

"I don't. It's a completely random process." That, like many things he said, was a lie. Most of the Time Lords could choose their appearance, but the Doctor had never gotten the hang of it. Not consciously, anyway. He would never admit it to the humans. Besides, what was the point of becoming someone else if you could completely control the outcome? He liked leaving it to chance. "How do I look?"

"Older?" Yaz was hesitant, searching for the right words.

"Not what I was hoping for." The Doctor quickly pulled out his phone and opened the camera, studying his image. What he saw was the last thing he'd been expecting.

His previous face.

That had never happened before.

Certain qualities might show up again, from one body to another. But a replica, that should be impossible, shouldn't it? He thought back. He had seen this face now twice before, the first time at Pompeii. He concluded he'd subconsciously chosen this face as a reminder to save people. Why had he chosen it again? "How did this happen?"

"You're tellin' me. Seems like yesterday I was in my thirties…" Graham started.

"Shut up, not-Bill." The Doctor cut Graham off, ignoring his frown. The repeating faces would be yet another thing to sort out later. Right now he had to assure his friend "Speaking of bodies, we should check out this dead one."

"Right." Yaz tried not to flinch as the Doctor came near her to look at the corpse. He gave her a slight frown of disapproval. Their Doctor could be a bit awkward, but she was never outright rude. What did regeneration mean? Was their Doctor gone forever? She didn't know what to think. "As I said, can't tell how he died. No bullet wounds, no blood."

"Good observations, Yaz," he said. He was pleased to see she smiled a bit. Graham shot her a look as if to say, _he remembers your name_? But before the Doctor could get a closer look, a clatter of footsteps filled the room.

"Stop, or we shoot!" A voice, female, commanded. The Doctor turned around, holding his hands behind his back as he surveyed the newcomers. Three of them. Soldiers, based on their matching grey uniforms. Like the corpse he'd been so rudely interrupted from examining, they looked human. That no guarantee they were. Lots of species resembled humans, including his own. It was a popular genetic template. He noted the rigid precision, the steely eyes, the comm pieces in their ears. They looked brutish, not keen on asking questions, or so much as paying attention. It would work in his favor. 

"Oh good, the welcoming committee. Mind putting out some extra place settings for dinner?" As he spoke, he typed a quick text.

"More looters." The same voice, with a snort of disgust. It came from a blonde woman, all angles and muscles. "We ain't giving you shit. You!" she pointed her gun at the Doctor. "Hands up!" The Doctor raised his hands, still holding his phone. "Give me that," the woman snarled. With a sigh, he handed over the phone.

"Look, this is a big misunderstanding." said Yaz, holding her hands high. She kept her attention divided between the Doctor and the soldiers. "Our ship broke down and we came in looking for help. We didn't kill this man."

"You didn't. I did." A tall, burly man came forward. "He broke in, looking for food."

"And you killed him?" Yaz was horrified.

"What and let the scroungers overrun us? They've taken out most of our squadron. We're already down to half rations." His expression was a mix of anger and sadness. "They keep breakin' in as if we've got a secret cache of food somewhere. Bunch of worthless leeches."

"What happened to their food?" asked Graham. He remembered the barren land outside and wondered if it was widespread. What had happened here? Perhaps there was something they could do to help.

"Where've you been, codger?" The soldier's eyebrows raised in confusion. "Been like that since the sun dissolved."

"Suns don't dissolve. Do you mean collapse?" The Doctor asked, trying not to let his contempt show. Once again his suspicions about the soldiers were confirmed. Small-minded, thinking of a starving person as a parasite rather than someone to be helped. People, regardless of the species, were the same all over. However, the sun dissolving-that was different. That was interesting.

"It dissolved." The man repeated, talking to him as if he were an idiot. "Planet's been dark for over a year. Riots and starvation killed most of the population, but there's a few survivors."

"Yet you were doing research here," The Doctor said. "We found the lab. What were you working on?"

"You don't get to ask the questions." The woman huffed. Her earpiece chimed. She spoke into a microphone clipped to her uniform. "Yes, we found them. Three of them. They are contained. Right away." After another chime of the earpiece, she brandished her gun. "Captain wants to see you. Let's go." 

Yaz and Graham looked to the Doctor, to follow his lead. With nonchalance, he took a few slow steps towards the door. Once behind her, the woman butted her gun into his back. Yaz hesitated, considering her options. If she made a run for it, they'd shoot her. There was nowhere to hide, no chance to grab something to defend herself. She fell in behind the Doctor and Graham, a strong hand clamped on her shoulder. The largest soldier, the one who hadn't spoken, was beside her, glaring. 

—  
Captain Trawker watched the confrontation between his troops and the intruders with exhilaration, a rare thing these days. This Doctor had a sharp mind, almost nearly as sharp as his own. No longer would he trapped here among these imbeciles! And the complete transformation of his appearance had been something else entirely. The Doctor was the key to getting out of this place.

He'd been so entranced watching the Doctor, he'd lost track of the fourth intruder, the tall one. His glance flicked over to the other end of the corridor, where he'd last been seen. No sign of him and his men were empty-handed so far. They'd find him. Nobody could hide for long on the base. He leaned back in his chair, putting his feet up on the console. When the Doctor arrived, they were going to have a stimulating discussion.

\--

Ryan hid in the lab storage closet, trying to hold still despite the metal pointy object jabbing him in the back. He'd heard heavy footsteps approach and loud, unfamiliar voices, and panicking, lunged towards the nearest door. The closet was tiny and packed, and there'd barely been enough room for him. He tried not to kick over the large metal pails. An almost fruity odor permeated the closet, and he wondered if he was being exposed to a chemical he shouldn't be. If he grew an extra arm, he'd have a hard time explaining that to his friends back home. The footsteps stopped right in front of him, on the other side of the door.

"Captain said 'ey came this way," he heard a deep voice, male, say slightly muffled through the door. A bunch of clattering and banging. "Don't see any sign of 'em."

"Think this is another drill?" The other voice, female, sounded exhausted. "Don't see why we need 'em. We took care of the one this morning with no problems."

Ryan held very still and hoped they ignored the closet door. He heard clattering and banging as they opened cabinets, along with more grumbling. The squeak of furniture being pushed aside. It didn't sound like they were coming anywhere near him. He was about to relax, just for a moment, when his phone buzzed in his pocket.

"You hear that?" The deep voice said.

Ryan held his breath. He didn't dare move. His heart threatened to burst out of his chest. He quickly pondered his options. Jump out, ready to fight? He wasn't that much of a fighter, and his pursuers were probably armed. The only advantage he had was surprise.

"Must be one of these bloody machines they forgot to turn off before they left. Hate bein' in here, place gives me the creeps," said his companion.

Ryan hoped they went with that train of thought. Yes, normal noise, nothing to see here, move along. Before her partner could respond, there was a loud creaking noise, from somewhere out of the lab.

"Heard that. Probably them." The second voice again, relieved.

"Let's go!" And with that, the heavy footsteps were off and running.

Ryan waited until the footsteps faded before stepping out of the closet, tension evaporating from him. It took a moment for him to remember his phone. A text from the Doctor: **Bring the blue crystal**. 

He knew which one she meant: a long, thick shaft, deep blue. It had caught his eye immediately when he'd entered the lab, though she hadn't mentioned it. Grabbing it from a high shelf, he turned it over in his hands. The surface was smooth and shiny, the material nearly opaque. Looking into it was like looking into the ocean. There was nothing notable about it he could see. Was this something to fix the TARDIS? 

Ryan peeked into the corridor. No sign of anyone around. He stepped out of the lab, holding the door to let it shut gently behind him. Carefully, he started down the corridor. He dashed out, keeping to the walls, ready to dart into another room if no one saw him. 

—  
Yaz got pushed again by her captor as she walked down the corridor, her shoulder complaining from where she'd been grabbed. She kept her eyes out for a chance to break away, but the large, burly one stayed close, nudging her every few feet. The soldiers said little, mostly grunting to each other. 

Another nudge, telling her to turn right at this junction. The base was a maze of corridors, and they all looked like the ones they'd seen at the entrance-shiny grey metal, making it difficult to get her bearings. There was signage posted at each junction, but they were walking too quickly for her to read them. Every so often, she heard a creak, like an old door, and she noticed the soldiers stiffen. 

"What's that creaking?" The Doctor asked. He'd been asking questions since they'd left the room with the body, all of which had been ignored.

"Prob'ly just something in the walls. It's an old base," the woman remarked.

"Really? Looks almost brand new. Love to get the name of your contractor," the Doctor said. For his cheerful tone, he got butted with the end of the rifle. Yaz wondered if the place was about to collapse. They'd left their helmets at the door. If the base walls were breached, nothing stood between them and the cold. How long would it take for all of them to freeze to death? She tried to look at the positives. They were all alive and unharmed, her shoulder pain notwithstanding. Perhaps Ryan had eluded capture, and he'd be able to….

"The other intruder! Up ahead!" called the burly one. She caught a flash of bright orange turning the corner before the large soldier grabbed her arm, urging her to run. So much for that. "You! Stop right there!"

Ryan broke into a run, but the chase was short and quick before they caught up to him. Guns pointed at him, he put his hands in the air. "Hedsop to Trawker, we've got the last one," said the burly one on his comm piece.

Ryan looked over his pursuers. Three grey-clad soldiers holding guns, and they had Granddad and Yaz. They were with an older man he didn't recognize, also in an environmental suit, and from the looks of it, he was also a captive. He didn't know what would happen, but he needed a way to evade them.

"Don't even think about throwing us in a cell. The Doctor will get us out." He tried to sound authoritative.

"Yes, you're right," said the stranger. "Good, you brought the crystal."

Ryan's brow furrowed in confusion. How did he know about the text? Was he working with the Doctor somehow?

Hedsop grabbed for the crystal, keeping his gun trained on Ryan. He held it up. "This a weapon of some sort?"

"It's mostly a distraction." With that, the man held up the sonic-the Doctor's sonic-and pointed it at the crystal.

The soldiers dropped their guns and clutched their ears, falling to their knees. The man's face twisted in slight discomfort before he shouted, "Run! Now!"

Ryan took off down the hall. The orange-clad man dashed in front of him, surprisingly fast given his age. Whatever misgivings he had about following an unknown man were overruled by the fact Yaz and Granddad were following him as well. That, and the three armed soldiers that would be behind them at any moment.

"Where are we going?" Yaz asked as the man led them through the maze of corridors.

"Looking for a good hiding spot. Ahh, there!" He soniced a manhole like cover on the ground, popping it open. "Everybody down!"

Yaz wasted no time climbing down the ladder runs attached to the wall. Ryan peered into the hole. It was so dark he couldn't see anything. Why did it always have to be ladders?

"Come on Ryan! You can do this!" The man gave him an encouraging smile.

Before Ryan could ask how the stranger knew his name, Graham gave him a push. "Go, son!"

As carefully as he could, Ryan descended into the darkness. Graham went next, followed by the stranger, who soniced the manhole shut. "That should buy us some time. Anyone want to turn their phone on? Helps to be able to see."

A moment later, Ryan had his phone out and torch on. Ryan looked at the man, who wore a self-satisfied grin. "So, you're probably wondering how I did that. The soldiers were so focused on you they didn't notice me pull out the sonic screwdriver. I used the crystal to create a vibration at a frequency that would overload their comm pieces. They're completely useless now. Well, the soldiers were useless to begin with."

The crystal. The soldier had dropped it, and he'd been too in a hurry to get away to pick it up. "I have to go back and get the crystal. I need to get it to the Doctor." He started for the ladder, but he felt a hand on his shoulder. He turned around. to see the stranger had grabbed him. 

"You already did," he said. 

"What?" Something was very strange here. "Where's the Doctor? And why do you have her sonic?" 

"Oh. I'm going to let one of you lot explain that." He gestured to Graham and Yaz. "I don't do repeats."

"Son, I know it's hard to believe, but this is the Doctor," Graham said. At Ryan's astounded look, he added, "She um, what's it called, she got a new body."

"Except I didn't. I have the same body that I did before. Before I met you. I've had fourteen different bodies, never had a repeat. Until now. And what's more, I feel like him. The man I was in this body." He slumped to the floor. "Never had this happen before."

Yaz remembered then a conversation form when she and the Doctor had first met, aboard the train from Sheffield. _Half an hour ago I was a white-haired Scotsman_. "How do you change bodies? How does it happen?"

"Normally, it happens when I'm dying. A little trick my people use. Nothing killed me this time, nothing obvious." The Doctor thought of the crawling on his skin. Was it his imagination, or had the crawling gotten worse again? Perhaps there was some kind of bug down here.

The word _dying_ hit Yaz like a sledgehammer to the head. She'd been hoping this was some sort of temporary state, that somehow "her" Doctor could be restored. If she'd died...she was too afraid to ask. Instead, she tried to focus on something else. "Can you live forever?" 

"Well no, not forever. There are limits." He didn't know how many new regenerations the Time Lords had given him at Trenzalore, nor was he inclined to find out today. He tried not to think about the crawling, tried not to grasp at his sleeves.

Ryan was still trying to wrap his head around what he'd just been told. "Why are you a bloke?" 

"Really? I tell you about an amazing feat of biology, and that's what you focus on?" the Doctor scoffed. "Humans, you're so small-minded."

Rebuffed, Ryan fell silent.

"So now what do we do?" Graham asked. "We can't hide out here forever. They're bound to come looking for us."

"We can't go back to the TARDIS yet." Ryan thought he detected a note of weariness. Maybe from the chase. "It's still unable to move. Besides that, there's a mystery about this planet. We need to figure out what's going on here"

That sounded like the Doctor, at least. Ryan slid to the floor himself, trying to get comfortable on what felt like concrete. They were going to be here for a while.

—  
Outside, the transformed bugs rammed themselves into the base walls, causing them to weaken and creak. The bugs, now the height of a child's bicycle, rammed again and again, with little regard for self-preservation. Some would be injured. A few may die. The rest would flourish.

Their mandibles were large and strong, easily able to break through what was left of the soil. They'd become so large and strong. The remaining micronutrients were no longer enough to feed them. But they'd caught the scent of food, and followed it to the base. The metal walls were strong, very strong, but they were stronger. The walls would not deter them from what they needed.

They were close. They were so close.  
—  
Ryan inspected yet another of the boxes that lined the walls, to find it was empty. Yaz had found a light switch by feeling around on the wall. They appeared to be in some sort of large storage area. Boxes lined the walls, which he and Graham were inspecting. So far they hadn't found much, mostly extra grey uniforms and empty boxes. The boxes all had the musty smell of neglect. 

"Penny for your thoughts," Graham said.

He realized he hadn't said much in a while. "You think that's really the Doctor?"

He looked wistful. "It's the Doc. She told us about this, your Nan and me. Harder to see it in real life though, innit?"

"Don't seem like her." 

"I know." Graham was overcome with a wave of sadness. Could you miss someone, even when they were right in front of you?

Meanwhile, Yaz paced through the perimeter of the basement, her third pass through. Not that she'd expected to catch anything she hadn't seen before. She noticed the boys kept sneaking glances back at the Doctor. Graham with apprehension, Ryan still mired in confusion. She suspected going through the boxes was an excuse to avoid him. Meanwhile, the Doctor remained seated, leaning up against the wall, expressions occasionally contorting in what looked like pain. In the three hours they'd been down here, he'd mostly said he was thinking, in a gruff tone that strongly suggested they not interrupt.

There'd been no sign of the soldiers yet, at least.

As she walked, she contemplated the Doctor. She didn't want to believe the perky blonde, was dead. She couldn't picture this man taking them on a bicycle race, or running through the beaches of Vega, basking in the sun. He was reserved, a bit cranky. He still had a mind that was beyond comparison. Was he still someone that she wanted to know? 

She shook her head at that. The Doctor was the most amazing person she'd ever met, regardless of form. And she knew above all else, the man sitting against the wall needed a friend. She saw the traces of loneliness in his eyes, reminding her of the look when "her" Doctor had when she dropped them off at home.

Breaking away from the cool stone wall, she took a few cautious steps and sat next to the Doctor, who simply watched her.

"Hi," he sounded not unfriendly, but cautious.

"Hi," she replied. They were off to a good start, at least. "What's on your mind?"

"Thinking that empty spot there might be a good place for a foosball table." He gave her a half-smile as he gestured. "Plenty of space. No puddles."

She gave a small chuckle. For a moment, they both sat in silence. "Don't mind the boys. Think it's a lot for them to handle," she said.

"And it's not for you?"

"It is, it's just…" _This feels alien, more alien than you ever have before, but you look like you need someone, Doctor_. At his penetrating gaze, the words died on her lips.

"Suppose I should be used to it. Humans have a hard time with change." He stared into the distance.

"I think we do change, but little by little, so it's hard to notice. " She thought of the girl she'd been in secondary, beaten down and ready to disappear, a far cry from who she was now. She couldn't pinpoint the moment that happened, just a steady stream of tiny actions that brought her to this point. "When it happens all at once, it's overload."

"Suppose I have to be a bit 'extra' about it. See? I can keep up with the kids." He tried to smile, but his expression turned dark. The crawling was getting worse, another crescendo. "Ugh…no."

Before she could ask him what was wrong, Ryan and Graham came towards them, each carrying a box. "Think we've found something. Machine parts."

"Finally, something useful." His eyebrows raised, and he leaned forward to take a look, but then cried out in pain, clutching his back. "No, no, not now, not while I'm…aaah!" He jerked upright. Sweat beaded his upper brow.

The men exchanged concerned glances. "Doctor, are you all right? Is there anything we can do?" Ryan asked.

"No," he dropped his head. "It's…" he held up his ungloved hands, showing the purple glow to his friends. He waved them away, signaling for them to stay back.  
The three humans stared helplessly, watching the glow spread down to his wrists, and presumably his arms. Yaz felt the urge to do something, anything, but she had no idea what. What was this light? Was this something on the base, or something else entirely?

A moment later, he disappeared in a burst of violet light, shining brighter than the dim lamp of the storage room. A scream filled the air. Ryan glanced nervously towards the ladder. If that didn't get the soldiers' attention….

The light stopped as abruptly as it began. In its place was a man with floppy hair and a large chin, decades younger than his predecessor.

"Is that.." Yaz began, at a loss for words. "Are you okay?"

"I am perfectly all right. Never been better," the man replied with a grin. "Nothing to worry about, not in the least. Trust me, I'm the Doctor."


	3. Chapter 3

**Summary for the Chapter:**

> On a barren planet where the sun has allegedly dissolved, a newly transformed Eleventh Doctor and the fam are hiding in the basement of on a military base, evading the resident soldiers. The base captain, who has his own agenda, watches them in fascination, Meanwhile, giant bugs are outside the base, trying to bang their way in.
> 
> What is happening to the Doctor?  
> How will they escape to find the parts to repair the TARDIS?  
> Does Graham still have that sandwich in his jacket?

**Notes for the Chapter:**

> Hello lovely readers:
> 
> This chapter took longer than I expected to get out, largely because this section ended up being much longer than I originally planned. The good news is the next chapter is close to being finished.

The Doctor stared back into the confused faces of his friends. Two regenerations in a matter of hours were much more than they could handle. He needed to reassure them, but first, he needed a moment. In an automatic gesture, he touched the base of his neck to straighten his bow tie, his hand faltering when he remembered it was absent. Right. He'd left those behind. Unless…his hand traveled up to his face, feeling around. The other hand reached for his legs. He didn't expect to find any more or less than two, but it didn't hurt to check.

"You want to see the new face," one of his companions said, extending his phone. His brain was still fizzing and bubbling, he couldn't remember the man's name. He'd have it in a moment. Wordlessly, he snatched the phone from his friend's hand, and his suspicions were confirmed.

The previous face, before Eyebrows. Braces and bowties. Jammy dodgers and Ponds and Van Gogh and cracks in time.

Once was a coincidence. Twice was impossible to ignore.

The humans were still staring at him expectantly. Time to get into action. 

"Hello again!" he jumped up, and his legs immediately gave out. The human, the one who'd given him the phone, reached out to catch him, a strong arm around his midsection.

"Ryan! Good catch!" The Doctor hugged him quickly, not wanting his friend to see the concern in his expression. He remembered how he'd run into the wall after he became Eyebrows. He'd chalked it up to regeneration sickness at the time, but perhaps this was something else, a de-generation sickness. Whatever this was, it was making him embarrassingly uncoordinated.

"You remember us this time?" The older man. Graham.

"Of course. I never forget anyone, Graham." Letting go of Ryan, he enveloped Graham in a similar hug. One more of his friends to see, watching him with caution. "And Yaz." He took a tentative step towards her, reaching his arms out to hug her as well. "My friends. No one I'd rather be trapped in a basement with than my best friends. Especially with another old face" His legs still felt like a newborn colt's. 

"You've been this one before too?" Yaz asked.

He nodded. "Seems like I'm going backward. In order. I'm not regenerating. I'm degenerating. No, that sounds wrong. Un-regenerating?"

The humans' concern turned to astonishment. "Does that mean you're gettin' younger?" asked Ryan.

"Yes. Maybe. I might be," he said.

"Why?"

"I don't know. It's never happened before. Maybe it's something about this planet, something in the air. Maybe it has to do with what they were investigating on this base."

"What about us?" Yaz piped up. "Are we going to age backward too?"

"I wouldn't mind bein' younger myself," Graham looked hopeful. "Make it easier to keep up with you lot."

"Speak for yourself, Granddad," Ryan said. "What happens if Yaz and I turn into babies?"

"Not to worry, I speak fluent baby. But just in case." He ran the sonic over each of them. Nothing abnormal in their cellular processes that he could detect. "Completely normal. All of you." It didn't make sense though. He'd never heard of something that caused de-aging. Different species had been working on it for years, youth being a prized commodity across all forms of sapient life. None of them had ever gotten it right. At least, not without causing massive physiological instabilities. But for it to just happen was entirely unheard of.

"So what do we do now?" asked Yaz.

"Let's start with what we know." The Doctor took an experimental step on his own, to stand between his friends. His legs held. "We're on a planet that's lost its sun. Dissolved. By a weapon? Possibly."

"The planet is, or was, inhabited," Yaz added.

"And they were doing some kind of scientific work here," said Ryan.

"And the place is guarded by trigger happy soldiers," Graham said.

"What do we have at our disposal?" The Doctor asked.

Graham gestured to the box he'd set on the ground. "Ryan and I found some things in here. Not sure what they are but they might be able to help."

"Yes. Show me." He'd been looking into the box just before he'd transformed. Now, the crawling gone from his skin, he was able to focus. Grabbing the box, he rooted around in it. His jaw dropped open. He couldn't believe his luck.

"Graham! You magnificent bloke!" Dropping the box, he grabbed Graham by both cheeks and kissed him.

Sputtering, Graham pushed him away, wiping off his lips in disgust. "Do not ever do that again!"

Yaz put a hand up to her mouth to stifle her laughter. "What are those?"

He held up a flat square. "This is a schematic of the base. And I can use these parts" he gestured to the box." to build a crude heat-seeking tracker," said the Doctor. "We'll be able to see where the soldiers are. Best to get on it straight away" He started towards a work table, only to fall, sprawled on the ground.

"Doctor! Are you all right?" Ryan asked.

"Think so, yeah." The degeneration sickness was longer lasting, this time around. Was it going to keep getting worse? One way or another, they had to repair the TARDIS and get off this planet soon. He could not go back to being a child, he was certain of that. Once as a Time Tot was more than enough.  
\--

The fam-or the "gang' as this Doctor liked to call them-watched as the Doctor assembled the device. They didn't say it, but they were keeping an eye on him in case he collapsed again.

"Can this de-aging or whatever it is do permanent damage?" Yaz whispered to them in hushed tones. "What if we have to start carrying him everywhere?"

Graham shrugged. "Don't know about you two, but I'm getting whiplash." 

"Still upset he snogged you?" Yaz gave him a cheeky grin.

"Not another word about that!" Graham snapped. "But this one, he's energetic and so touchy-feely."

"Yeah. How many more changes will the Doctor go through? " Ryan said. His Doctor mostly gave him pats on the shoulder, and he found the sudden increase in affection unsettling. It wasn't that he wasn't an affectionate person himself. There was something about it that bothered him, but he couldn't put his finger on what. 

"Let's start it up. This will allow us to see the positions of everyone at the base." He flicked on a switch. "Oh, this is good news. Great news! Look!" He pointed to the screen. There were a series of blue dots scattered throughout the display. "There's only six life signs here, besides us. Place isn't overrun with soldiers. He picked it up. "We'll be able to track their position and avoid them."

"That's right. They said a lot of the squadron had been lost already. To people breaking in for food." Graham pointed out.

"What's this out here?" Ryan asked, pointing to some large globs at the edges of the map.

"Not sure. Perhaps there's another life form. Looks like it's outside the walls of the base," the Doctor said. 

"Maybe it's an animal. Like space cows," Graham said.

"Space cows?" Yaz raised an eyebrow.

"Well, not a space cow, but somethin' like that." he shrugged.

Something nagged at Ryan. If the sun had dissolved, there was no food-what would a space cow feed on? But it seemed like the Doctor had moved on.

"Let's get upstairs and take a look. " The Doctor started for the ladder rungs.

"What? Now?"

"We can't stay down here forever. Six soldiers, we can take them on."

"Have you got a plan?"

"Not quite. I've got a thing." With that, the Doctor started up the ladder. The humans, reluctant, followed suit.

\--  
The Doctor and his friends walked through the empty corridors, with him consulting the tracker to keep them away from the soldiers. He poked around at everything, sticking his head into empty rooms and inspecting random objects.

"What are you looking for?" Ryan asked. The creaking they'd heard before was back. He hadn't heard it down in the basement. It was creepy, like an old door opening in a horror movie.

"Answers. Parts. And let me know if you see a fez." He touched the front of his neck again. Yaz noticed he kept doing it, then giving a slight shake of his head after doing so. It was like a nervous tic.

Most of the rooms had nothing of note, until hey came up to a large, locked door. "Important things behind big locked doors. Let's take a look." After a whiz from the sonic, the door opened with a whoosh.

Inside, the room was larger than any others they'd seen. The ceiling was domed glass, in black oblong framed panels. The dark sky loomed above them. Machines with blinking lights were stacked along the walls. A large telescope, of sleek, black metal, on a small raised platform, was the focal point of the room.

"Reminds me of the planetarium." Ryan stepped in, looking up.

"That's more or less what this is, Ryan." The Doctor spread out his arms. "An observatory, watching the planets in real-time." He looked up, squinting. "Not that we can see much at the moment. There's not much to look at with the naked eye. Let's have a look, shall we?"  
As the Doctor peered through the telescope, the humans spread out, walking around the room. Yaz made a point of studying all the equipment, inspecting everything closely. Graham copied her movements, but he wished he knew what he was doing. He'd never been much of a techie, largely relying on Ryan every time he needed to upgrade his phone. He was careful not to touch anything or even look at it funny. One of the monitors he passed turned red and emitted a slow, beeping noise. He took a closer look. Wall integrity decreased. That didn't sound good. 

Approaching the platform, he looked up to the alien. "Hey Doc, there's…."

"Not now." The Doctor held up a hand, silencing him.

"What is it? What have you seen?"

"Nothing. That's the problem." The Doctor turned to him, boring holes with his gaze. "I started off looking for what happened to the sun. If a star burns out, it leaves something behind. A dwarf star, or a black hole. Even if the sun went nova, we should see something. But there's nothing."

"What would cause that?"

"I'm not sure. There's something I'm missing though. Something important. Very important. Still trying to figure it out." The Doctor went back to the telescope, typing frantically at a keyboard below, pushing buttons at the side. He tapped his fingers to his head, muttering under his breath. "Come on, think, think." Suddenly, he threw his arms in the air! "Yes! That's what it is!" He casually jumped down from the platform. "Everyone! Come here!" 

When they'd surrounded him, he began, "First, can I just say I'm extremely clever?"

Graham tried not to roll his eyes. This Doctor had no shortage of ego.

"When I looked through the telescope, there were no stars, no other planets. I could only see one thing: nebulae. The beginnings of stars, gaseous clouds coming together to take shape. I like a nebula as much as the next person, but to have so many of them, it made no sense. So I expanded the telescope's range, and I kept looking. And I bumped into the edge of existence. We're near the edge of the universe. Not only that, but the edge is moving. This universe is contracting. Which it only does at the end."

The statement loomed over the humans like a rain cloud. The end of the universe sounded like a poor prospect for parts to repair the TARDIS and a lesser one for surviving. But the Doctor's maniacal grin gave them a flicker of hope.

"Except I've been to the end of the universe. I've made several trips. It doesn't look like this. And the readings, the surrounding hydrogen levels are too high. The radiation levels are too low. It's all very, very wrong." A gleam of delight was in his eyes. "This isn't our universe." 

At his friends' confused expressions, he pointed to a display next to the telescope. "Based on the readings, this is a pocket universe. A small bubble, produced by the cosmic expansion of our existing universe." His smile fell as he remembered the last time he'd been in a pocket universe, looking for the Corsair. Somehow the memory was as fresh as the day it happened, likely to do with the younger body. He steeled his resolve. None of his friends would die this time.

"It's not ending anytime soon, is it?" Ryan asked.

"Only in cosmic terms. There are a few decades left at least," The Doctor assured him. "Still, there's some things that don't make sense. Why would there be nebulas? There shouldn't be enough energy left in the universe for them to form. Why would…"

His words were interrupted by a bang against the wall. "Wall integrity compromise imminent." A computerized voice announced.

Graham thought back to the warning he'd seen. The bang sounded again. "It's coming from over here!" Ryan said, running to one of the rare areas of bare wall. The banging was coming louder, echoing through the room.

The Doctor rushed over, sonicing the wall. "Something's trying to break in!"

"The space cows," Ryan said. "What do we do?!?" Frantically, he looked around for something to hold them off, but there was nothing other than some desk chairs. He grabbed one anyway, wheeling it towards the sound of the banging. As he pushed the chair against the wall, an imprint formed in the wall. Whatever these things were, they were strong.

"You think that's going to do anything?!" Graham said.

"What else do we got?" Ryan snapped back at him. With every bang, the creaking he'd heard earlier was getting louder.

"Still working on it." The Doctor kept sonicing the wall. "Trying to get a reading, but I can't. The wall's too…"

"Freeze! All of you! Hands up and step away from the wall." A group of the grey-clad soldiers came running into the room, pointing their weapons. Yaz recognized three of them as the ones who'd captured them earlier, along with two she didn't recognize. She counted five soldiers, which meant this was every person at the base. Except for one.

The Doctor slowly held up his hands, the humans following his lead. The leader, the muscular woman who'd captured them earlier, slowly inspected them, lips curled in a sneer. "You lot ain't beggars, are you? Trying to sabotage our equipment? You're terrorists!"

Yaz prickled at the last word, but Ryan looked back towards the repeated, rhythmic banging on the wall, the repeated blaring warnings from the overhead speaker. "Umm, mate? Think there's something more pressing than us."

"Silence!" she commanded. She waved the burly man into the direction of the banging. "Hedsop, go see what that is!" Turning her attention to the captives, she asked, "Where's the other one? The old man?'

"Long story. I'd tell you, but you lot don't seem much for listening." The Doctor smirked.

She glared at him. "And where'd you come from? How many more of you are hiding on this base?" 

The Doctor kept his hands up, not moving. "And what is it we're not supposed to see here? Something you want to hide?" He almost seemed amused by their standoff.  
She pointed her gun at his head. "You've got five seconds to answer me, or you're going to get it." She cocked the gun. "Five, four, three..:  
She was interrupted by a loud crash, followed by a trail of cold air. Everyone's heads snapped in the direction of the noise 

A gigantic insect head had broken into the observatory wall.


	4. Chapter 4

**Summary for the Chapter:**

> The Eleventh Doctor and the fam are in the military base observatory. The Doctor has just discovered they’re in a pocket universe. The base soldiers have them pinned down, while a giant insect’s head has broken the base wall open.

**Notes for the Chapter:**

> This chapter's going to get gory. Strap in.

"What is that?" the Doctor asked, nodding to the insect.

The soldiers' leader looked shaken. "I don't know." 

The insect was still trying to push forward, cracks forming in the metal. Deceptively calm, the computerized voice provided the most unhelpful alert in existence: "Alert. Wall integrity compromised. Wall integrity compromised. Wall integrity compromised." 

A thought hit Graham like a sledgehammer. They'd all freeze in minutes from the cold air coming in from outside. The soldiers' attention was still focused on the insect. He caught Ryan and Yaz's eye and nodded towards the door. He tried to subtly move in its direction, but the guards' glares kept them in place.

Slowly lowering his arms, the Doctor pointed the sonic at the insect head. He looked at the reading, brows furrowed in confusion. "Is that right? Can't be. Let me get a closer look."

"Stay where you are, smart man." The leader, nerves recovered, addressed him through clenched teeth. "Hedsop, go check it out." The other three soldiers kept their weapons pointed at the captives. 

Hedsop took a close look at the insect head. "Looks like a Joam bug, but bigger. How'd they get so huge?" He held out a hand to touch it.  
Which promptly got snapped off.

Hedsop's scream was followed by the crunch of bones as the wrist was severed by the bug's giant mandibles while still trying to bang forward. The insect took slow, thoughtful bites, mangling what was left of his hand. Hedsop was rooted to the spot in shock.   
Snapping out of their horror, another soldier ran to Hedsop. "Fuck man, thats fucked up." He quickly pulled off his shirt, stuffing it at the edge of Hedsop's stump.

"My hand! My hand!" Hedsop shrieked with a pitch that could shatter crystal. The blood immediately soaked through the makeshift bandage.

"Hang in there, Hedsop." He edged away from the insect head. "This is fucked up shit. We're going to get you to the infirmary and…"

He never finished his sentence. The wall gave way and there were three large bugs on them at once. They knocked the two men to the ground, their mandibles digging into the men's abdomens with a squish. Dark blood flushed out in pools around them. 

Seeing the flash of steel, Graham grabbed Ryan and Yaz's arms, pulling them out of the way as the soldiers began shooting. The laser blasts took out the insects' legs, wounded their exoskeletons, but did nothing to stop the horrible chewing noises. While the soldiers kept shooting, another insect clambered over them, its long, hair thin antennae twitching. The soldiers' shouting to each other was barely audible over the screams of the insects' victims. The humans crouched to the ground, avoiding the crossfire. Graham couldn't bring himself to look in the direction of the insects. 

The Doctor was a steely calm island in an ocean of chaos. "Everyone. Out. Now." 

"I give the orders around here," The leader said.

"We can argue about the chain of command or we can live. Out!" 

Everyone stampeded towards the door as if the bugs would be on their tail at any moment. The bugs, having found a feast, were in no hurry to follow. As soon as the last person was out, the Doctor soniced the door shut. Yaz leaned against the wall, her insides quaking. She'd seen gruesome things at work-auto accidents, suicides, industrial accidents. Nothing had prepared her for that. She took deep breaths, trying to calm herself. The surviving soldiers looked grim, as they stared back at the door. Despite the thickness, muffling crunching and cracking could still be heard from the other side. 

"Good seal, here," The Doctor nodded to her, catching her frightened look. "It'll keep the cold out."

"And the bugs?" Graham asked. "Ryan saw a bunch of blobs on the thermal whatsits earlier. Did you grab that?"

"No, got a little distracted," The Doctor replied. When Graham gave him a look, he gave an unapologetic shrug.

"What in the world are those things?" Ryan directed his question towards the soldiers.

"That's what we want to know." The woman surveyed them, arms crossed. "What have you done to them?"

"We haven't done anything." Ryan protested, a sharp edge in his tone. "We came here lookin' for help, and we keep getting attacked. And you're blaming us." He clenched his fists. Guns or not, he was furious enough to start throwing punches.

Noting his ferocity, Yaz interrupted. "Doctor, what did you find out when you scanned it with the sonic?"

"It was covered in traces of Hawking radiation." The Doctor narrowed his eyes, focusing on the leader. "It's given off by black holes. We're nowhere near a black hole. Nowhere near anything.

Hedsop called them Joam bugs, meaning they must be local residents. The work being done here, you were messing about with growing bugs, weren't you? A potential food source for your starving population. But then you lost control, which is what you get when you start playing with things you don't understand. I should know."

"That's ridiculous." The leader gave him an indignant glare." Why would we eat Joam bugs?"

"Insects are a delicacy in numerous civilizations throughout the universe," The Doctor said. "These Joam bugs, tell me about them."

"They're one of the few animals that's still alive on this forsaken planet," grumbled one of the soldiers. "Except they're smaller. Much smaller. Like this." She held up her thumb and forefinger. "We don't see a lot at the surface. Mostly they burrow underground, trying to stay warm." Her expression turned grim. "We're in big trouble. Joam bugs can survive practically anything. Storms, cold, heat, near starvation-they're very difficult to kill. You saw how little effect our laser guns had on them."

"Like cockroaches," Graham muttered. "Giant alien cockroaches."

"Giant alien man-eating cockroaches," Yaz shuddered, thinking of the eaten soldiers. The spiders at Mum's hotel were nothing compared to these things. Being reminded of the spiders gave her an idea. "Maybe there was something here that caused them to grow? Chemicals or something like that?"

"Why would we make Joam bugs that would attack our base?" she said accusingly. "And If you didn't create them, who did?"

"All of you, stop it, now." The Doctor was stern. "We're stranded on a dead planet, trapped on an understaffed, unprepared military base which giant bugs are threatening to destroy, yet you keep trying to attack us. I've had enough. If we're going to get through this, we need you to put those bloody guns away."

The leader hesitated, clenching her jaw, but after another glance at the door, she relented. "Stand down." She ordered the two others, as they holstered their weapons. Yaz looked at the Doctor, trying not to show her surprise. The Doctor's dislike of guns was nothing new, but she'd never heard him (or her) give a lecture like that. Normally, the Doctor inspired a lot of feelings in her, but this was a new one: fear. It was like being lectured by her precinct captain, only worse.

"That's better. You," he pointed to the soldiers' leader. "Start talking. First off, I want your names."

"I'm Pasha. This is Kyla and Norven." She nodded to her fellow soldiers.

"I'm the Doctor. This is Ryan, Graham, and Yaz. My gang." The Doctor tented his fingers, giving a slight smile. "Tell us everything you know about this base. What are you protecting? What are you studying here?"

Pasha sighed. "When the sun first went out, they gathered the planet's top minds here to find an alternate source of energy, something to keep the crops growing. They worked day and night but found nothing, nothing that would supply the energy to keep a planet alive. It was terrible; they fought amongst themselves constantly. Finally, after months, they came to some sort of truce. They announced there were energy sources available on other planets, and needed spacefaring supplies. They set course six months ago. Our job here is to guard their work, make sure nothing is disturbed until their return. To keep out the scroungers." She gazed over them. "Though you lot don't look much like scroungers. Too well-fed. Those suits look almost new. Mega rich? Secret bunkers and all that?"

"We're not locals," the Doctor said. "Arrived here on a spaceship. Which is in need of repair."

Pasha's eyes widened. "Aliens? Never met an alien before."

"Well, you have now." He reached for the front of his neck again. "We're not from this planet. We can get answers. If you let us."

Pasha looked skeptical. "I need to talk to the Captain. If only that idiot hadn't shorted out my commpiece." The Doctor's lips twitched at being called an idiot, but he held his tongue. No reason to enlighten them further.

"Mine still works." Norven touched his ear. "Captain, we're here with the intruders." Silence. "He's not responding. Think the bugs got him?"  
"It's unlikely. The command center is in the middle of the base. They'd have to chew through a lot of steel," Pasha said. Addressing the Doctor, she asked, "Can you restore the sun? It's a slow path to starvation for all of us." There was a note of fear in her voice.

The Doctor hated to abandon anyone. And despite their weapons and their attitude, he could see how vulnerable they felt. However, even he had limits to what he was capable of doing, and a sun was well beyond that. He wondered how much the soldiers knew about the state of the universe. If he told them the truth, he'd be risking their cooperation. Experience had long shown him repeatedly people with nothing to lose were also the most dangerous. Given the state of the base, he concluded they were also adept at survival, which is exactly what he needed right now. He suspected there was more happening in this universe than he realized. He still didn't know what was causing him to de-age. If only he'd had more time in the observatory, he could have figured it out. 

He straightened up. "I can look for answers. Ryan and I found one lab already. I'm guessing there are others." 

Pasha nodded. "The main one is towards the back of the complex. But first, we're going to need protection in case of more bug attacks. Follow me."

\--  
Captain Trawker did not respond to the comm. He had no need of the soldiers, as they no longer served his purpose. Instead, he was focused on the long-range sensors. Designed to warn of attacks on the base, they had long gone unused when the planet had gone dark. Until now. 

His hands were steady on the control knobs, turning them ever so slightly to weed out noise. This crude equipment required agonizing precision. But with the correct amount of manipulation, the slightest touch, he could find what he was looking for. It would take time. But time was the only thing he had in abundance. He had the skill. He had patience. He had the brains to figure a way off this base.

Minutes ticked by. The only sound in the room was the hum of the equipment and his slow, steady breaths.   
And then. 

A beep.

There. There it was. An object showed up on the screen, a red rectangle on an otherwise black screen. Based on the readings, it was about 3 meters tall and half as wide. The intruders' ship. The TARDIS, they'd called it. He'd assumed their spaceship would be bigger. Perhaps it was a pod of some sort, or the rest was undetectable by this obsolete junk.

No matter. He would find out soon enough. 

A plan was beginning to form. His seat gave a gentle squeak as he rose, retreating to his quarters. Kneeling before his bunk, he pulled out his cache of weapons, stored in an unassuming wooden box. He'd taken them from the general inventory, one at a time as to escape notice. They were about to come in handy. 

\--

The group walked down the hall in uneasy silence. The computerized alert system was quiet, but the occasional creaks continued. Ryan wasn't sure where they were in the maze of corridors. None of them had windows, so it was impossible to tell whether they were near the outer wall or not. He hoped they were as deep inside the base as possible. With every creak, he jumped, worrying the bugs would appear in the corridor. He needed a mental distraction, but not too much of a distraction. From the expression on Nyla's face, she could use the same thing.

He sidled up to her. "Have you been at the base long?" 

"Arrived about a year before the sun went out. The military provides free training to those who can't afford paying into a school or an apprenticeship, in exchange for two years of service. I was going to take over Mum's repair shop." she said with bitterness. "Doesn't exist anymore. Neither does Mum."

"I'm sorry," said Ryan, and felt a pang of loneliness, thinking of his own mum. 

"Are there any other bases nearby?" The Doctor asked. He tried to ignore the now-familiar crawly feeling that lodged within him. He should have a few more hours before the next de-aging, at least. 

"Nearest one is over 500 hundred clicks away," Pasha replied. "They went down early. Overrun by scroungers. We've tried contacting others but haven't received a response in ages. This one was the most heavily guarded, because of the scientific work. Here we are." she stopped in front of a cupboard. 

The slim door opened with a click and swung open to canisters of various sizes. Pasha pulled out three identical glass tubes that resembled brown caulking guns. "This is Atrom gas, the only insecticide that works on Joam bugs. It is extremely poisonous. If you come in contact with it, you'll be dead in minutes." She pointed to a handle on the back, instructing her fellow soldiers. "When approaching one, push down and it will let out a stream of gas. Also, be very careful with that casing. It's glass. Atrom gas corrodes metal, so be careful around machinery as well."

Graham's eyes locked on the brown gas in the casing. He looked to the Doctor, who watched the soldiers with dispassionate interest. He thought at first the Doctor might object to killing the Joam bugs, but he was letting this slide. Maybe it was something about this version of him. Or maybe it didn't matter. He'd noticed the Doctor's morality tended to be flexible, regardless of the incarnation. 

After handing her charges gloves, Pasha also withdrew a small glass vial, placing it in her breast pocket. "The antidote. There's not enough for all of us. Be very careful. Now let's head to the main lab."

They moved quickly down the corridor, Pasha and Norven in the lead, Kyla bringing up the rear, poison casings in hand. At one point, the Doctor stopped, slipping away from the group, to examine something on the wall with the sonic, Yaz bounced on her feet, ready to run if the bugs showed up again. Despite the soldiers' presence, she felt vulnerable.

Ryan peered over to see what he was examining. "Any more Hawking radiation?" 

"No, but getting some strange readings. Reminded me a little of the ones from the TARDIS earlier. I suspect she knows more about this planet than she's letting on."

The mention of being in the TARDIS earlier felt like a stinging blow, a reminder of the Doctor he'd lost. Even though he knew the floppy-haired man beside him was the same person, he couldn't help feeling abandoned. He knew it wasn't fair, but couldn't shake the feeling either. It was like Dad all over again. 

"There's the lab door," Pasha announced, pointing to a large doorway at the end of the hall. The door, Ryan was relieved to see, looked similar in size and strength to the one at the observatory. "I just need to enter the security code. Pasha flipped open a control panel to the side. After punching in a set of numbers, she looked back at the group, noticing the Doctor was not with them, but halfway down the hall, crouched on the ground. She hadn't even noticed he'd slipped away again. "Doctor, what are you doing back there?"

"Checking one more thing." he was sonicing a small puddle on the ground. 

"Come on, Doctor!" Pasha called.

"Be there in a sec, something fascinating here." The Doctor scanned the puddle again. It was water and washing up liquid, but there was something unusual about the molecular structure, something he couldn't place. He'd seen a similar pattern in the wall, but it hadn't been exactly the same. Maybe it had to do with the outside temperature. Some alien elements native to this universe? 

His thoughts were interrupted by a clicking and a hiss, as a Joam bug turned the corner, facing him. 

Slowly rising as to not make any sudden moves, he watched as the bug approached, clacking its mandibles in a steady rhythm. He was vaguely aware the others were shouting for him to run. Excellent idea, running. He turned and ran, but heard the clatter of legs after him, growing closer, catching up. A hiss at his heels pushed him to run faster. He heard the clicking just behind him, and a snap of the mandibles and a burst of pain in the back of his lower left leg, and the hot rush of blood gushing down. He gritted his teeth with every step, trying to keep his pace. 

Kyla came charging towards them, casing in hand. She couldn't use it until he was clear of the bug. He tried to put some more space between him and the giant insect, as best as he could on his bad leg. He managed to dash past her, only to look back in horror.  
Blood seeped out from the center of her back. The Joam bug had pierced her middle. She stared down in horror for a moment before her eyes rolled back into her head. She dropped the casing, which made a loud crack when it hit the floor. The glass holding the Atrom gas was broken. There was a good chance as a Time Lord, he was immune to its effects, but this was not a good time to find out. 

"Everybody, in!" Pasha shouted to her gaping companions. Limping, the Doctor reached the lab door and soniced it shut once everyone was inside.

"Jeez, Doc, I thought you were a goner for a second. "Graham looked relieved. "Don't know how you pull it off."

"Neither do I, sometimes." The blood was already seeping through the environmental suit. Feeling with his hand, there was a large, thin slash in the suit leg, and he could feel the hot, sticky blood underneath. He took a quick glance around the lab, a dimly lit, large room filled with scientific gadgetry. He needed to start investigating. But at the moment, he was having trouble focusing. 

"Umm, Doctor?" Yaz examined the back of his suit. "That purple glowy thing you did before? It's happening again, on your leg."

"What? That can't be. Didn't think I was due yet, at least for a while," he said. But the light had spread to his hands. "The increase in metabolism caused by cellular repair must speed up the process." He should sit down. He looked around but couldn't see anything even passing for a chair in the dim light. He settled for leaning against the door, bracing for what was coming next. His companions, surrounding him, exchanged worried glances, as they wondered who would be in his place next. 

And then he changed. 

When the screaming subsided, a dark-haired man with broader features and sideburns was standing in his place. He would have known which one he was by sequence, but he could tell by the feel. The weight on his soul, the horror of war barely eased. The loneliness that ran through him despite being surrounded by his closest friends. The maddening urge to get up and move, run, anywhere and everywhere. In the mix of emotions, one stood out above the rest: gratitude. This version of himself, the one who hadn't wanted to go, had a second chance, albeit brief.

"Oh, this one. Rather like being this one." He grinned at his companions, flashing a mouth of white teeth. "Hello again."


	5. Chapter 5

**Summary for the Chapter:**

> Recap: Joam bugs are roaming the military base, eating whatever people they can get within reach. The Doctor and fam are hiding out in the main laboratory with the two surviving soldiers after outrunning one. Just prior, a glass canister of poisonous gas was dropped, cracking open in the corridor outside the lab. Eleven sustained a minor injury while running from the Joam bugs which accelerated his-deaging, causing him to become Ten. Meanwhile, Caaptain Trawker has located the TARDIS on sensors and is putting a plan into action.

**Notes for the Chapter:**

> Hello, lovely readers! Sorry this is later than I planned. I went back to onsite work a couple weeks ago on a part-time basis and it's been exhausting. This chapter is one of the most difficult ones I've ever written, largely in terms of figuring out the action.   
> Also, I'm throwing out S12 canon by the barrelful, with mentions of the Time Lords and the Time War. Also also, I didn't realize until today "enthalpy" was misspelled in the title, and I"m horribly embarrassed. It's corrected now.

Yaz took in the smiling man slowly, like a scared animal, even though at this point, he was the more vulnerable one. So far, he seemed friendly. Upbeat, but there was smoldering darkness in his eyes, something just beneath the surface. Loneliness. She knew all too well first impressions could be deceiving, and every Doctor was a question mark. She'd noticed he hadn't reached for his neck once. She knew he'd need a few minutes to get his bearings. She waited to see what he did next.

She was snapped out of her thoughts by Pasha. "What just happened?" she said, pointing at the Doctor. "Do you have transporter tech? How did he switch places with the Doctor?"

"This is him," she said. At their matching expressions of disbelief, She gave a brief explanation to Pasha and Norven about what had been happening to the Doctor. She hoped it was clear, given that she didn't fully understand it herself, but this Doctor kept nodding, so she must be on the right track.

"That's impossible. No one can do that." Pasha shook her head.

"Ma'am, the Doctor is the definition of impossible." Graham chimed in, keeping a cautious eye on the Doctor. He was still silent, sitting in a chair and taking in the lab.

"You're lying." Pasha put her hand on her weapon. "Tell me what really happened, or I'm marching you back out there to face the Joams unarmed."

Yaz thought quickly. Turning to the Doctor, she held out her arms. "Your leg." When he lifted it to waist level, she showed them the tear in the back of the environmental suit. "Here's where the Joam got him. Same tear." But there was nothing but pale, whole skin underneath.

"But no wound." Norven narrowed his eyes.

The Doctor cut in. "Time Lord bodies, very good at fixing cuts and scrapes. Heal much faster than normal, even when I'm not-deaging." He pulled down his leg. "And in this case, I got a whole new body, fixed up and ready to go." He stood up, wobbled, and collapsed again. "Almost."

Some things never changed, Yaz noted. The Doctor was always impatient.

"Then he was the old man too, wasn't he?" Pasha looked like she was ready to rip out his throat. The one that broke our comms. What other fancy tricks do you have?" She said accusingly.

"None." Ryan stammered.

"We're not trying to trick you, we just want to get our ship fixed." Yaz crossed her arms.

As Yaz and Ryan argued with the soldiers, the Doctor's brain function congealed. They were in a big room, it looked almost like a lab. That's right, it was a lab. He was here with the gang and three soldiers, and they were going to find the…

No. Two soldiers, he corrected himself. Kyla was gone. 

Hearts raw, his mind flashed back to Jenny. His daughter.

Well, somewhat his daughter. She'd been more a product of the fabrication machine than anything else. But her death hung on him as heavy as if he'd raised her himself. Dying from putting herself between him and a bullet. Children sacrificing themselves for their fathers was the wrong order of things. He should have saved her. 

This was who he was. Going through this deaging, revisiting, was like peeling back the layers of an onion. Seeing himself for who he was. The man who failed to save his friends. His family. Now he'd gotten his friends trapped on a dying planet. He would not allow them to die here, whether from self-immolation or his own carelessness. He would save them, no matter what the cost.   
The arguing voices around him reached a crescendo, though he'd tuned them out, overcome with grief. There was nothing to be gained by dwelling on it now. He stood slowly, lest his legs give out again.

"I'm the Doctor," he announced. The others stopped and watched with anticipation. For once, he wasn't sure what to say. Empathy, however, rarely steered him wrong. "I'm sorry about Kyla." 

Pasha pursed her lips in a thin line. "She knew the risks. It's part of the job." A feeble reassurance, more to herself than to him. Emotional armor, well-worn after losing so many of their numbers. But he wasn't having it. 

"No, it's not." He raised himself straighter. "Her death was senseless. Needless. Preventable. Just like so many others." He leaned against the wall, weary from the weight of the memories. "She was important, and don't even talk like she wasn't. She almost would have made it if she hadn't dropped the—" he stopped in mid-sentence, snapping to attention. "The canister cracked. It must have spread the gas all over the hall." He drew himself close to Pasha, nearly touching. "How good is the seal on this door? Is there any way to ventilate to the outside? What about in here? Can we make more of that antidote?"

"Slow down, " Pasha said. "Why would the gas fill the hall?"

"What?!" Surely, these soldiers weren't that daft they didn't understand the states of matter. "It leaked out the crack."

"Why would it?" Pasha looked back, puzzled.

The Doctor was going to make a smart retort, but something from his earlier scans clicked into place. His brain was still getting up to speed. There was a risk to be taken, but he'd never shied away from those. "Can I go back out there? Take a look?"

Pasha looked uncomfortable. "There might be more Joams." At his insistent look, she added. "Only if I come with you."

He spread out his arms. "Lead the way." Ignoring his friends' worried glances, he followed her out into the corridor. 

The Doctor trudged down the hall, boots heavy on the ground. He missed his trainers. A dark pool of cabernet-red spread on the concrete floor. The Doctor guessed that was all that was left of Kyla. He was secretly relieved-he always felt a clench of sadness at dead bodies, despite having seen billions upon billions of them. When the day came, that bodies became routine, it would be the beginning of his end of him, no matter how many regenerations he had left. A few chewed metal parts lay on the floor next to the blood. The Joam bugs must have consumed everything organic. 

The canister had rolled over to one side of the wall. He noticed a small wisp of brown gas. "Don't get too close." Pasha put a hand across his chest.

He crouched down a meter away from the glass to sonic the contents, using the setting for chemical composition. "The gas is no heavier than air, yet it stays on the ground and contained." He spoke mostly to himself. Pasha watched him with skepticism, hand on her chest in case she needed to grab the antidote vial. 

He tried another setting, this time looking at molecular structure. On a hunch, he tried a third setting.

That's when it clicked. He understood everything that was happening here. He turned to Pasha, a wide grin spread across his face.

"Satisfied?" she looked impatient.

"More than satisfied! Amazed! Stupefied!" The canister, the gas-no, this universe-was one of the most incredible things he'd ever seen. He couldn't wait to tell his friends about it. Trying to contain his excitement, he rose slowly as not to disturb the gas. An air current could still dislodge enough to kill them. 

"Over the gas?"

"Not just the gas, but to the answer to everything that's happening here! Can we get something to pick this up? Maybe something in the lab!" He clapped his hands." Poison gases, not a good thing to have to lie around!" 

—  
Ryan watched as the Doctor buzzed with maniacal energy, searching through closets and cabinets to find what he was looking for. He'd been relieved to see the Doctor and Pasha back in one piece, but he hadn't explained anything, just that he had to show them something. He had no idea if the Doctor had stumbled upon something exciting, or if this was how he normally was. 

When the Doctor was ready, he called them all over. They were standing in front of a clear box, not unlike the one he'd seen in the lab when they first arrived. Ryan jumped back when he saw the cracked canister inside.

"Not to worry, this is a sealed container. No danger here, not even if I do this." A lever hung from the top of the box. Using controls on the front, the Doctor slammed it on the casing, which elongated the crack, breaking it open.

But the gas remained in the same cylindrical shape.

"Doc, what happened? What kind of funny gas is that?" Graham asked. He hoped the explanation wasn't too complicated. The Doctor tended to ramble on at length about things that didn't make sense. 

"The gas is perfectly normal. It's this universe that's all cockeyed." Grabbing a thick marker, he moved to the wall, next to the box, writing in large letters. "In our universe, molecules are constantly in motion, in gases more than any other state of matter. Atomic structure is a chaotic ballet of movement. But not here. The molecules arrange themselves in order. In the gas. In the puddle. In the walls." 

"So what does that mean?" Ryan was squinted at the wall, trying to understand. It had been a few years since he'd taken chemistry. He glanced at the soldiers. Pasha looked furious he was writing on the wall, but she had yet to stop him. 

"Great question, Ryan!" The Doctor pointed at him. "It means, in this universe, time moves backward."

Graham shook his head. That made no sense. "Time moving backward? How'd you get that from all that molecule stuff? It ain't moving backward on my phone." He held it up.

"Graham, minutes, hours, days-those are all human constructs. Why twenty-four hours a day? Why not ten? Why not fifty? It's a collective fiction, like money, or America being a great country. The true rules of time are written in thermodynamics. The direction of entropy. Every piece of matter in our universe is on a singular course. To react. Maximize enthalpy. Increasing entropy, a one-way path towards the heat death of the universe. But here, in this little, beaten off the path, incredible universe, entropy is decreasing. Look! Isn't this amazing?" He pointed at the soldiers. "A pocket universe where time not only moves backward but with parallel sentient life development. You're this universe's version of human." He grinned.

"And that's why you're de-aging," Yaz said.

"Exactly!" The Doctor pointed to her. "I'm sensitive to changes in the flow of time, being a Time Lord and all. For you humans, it's not even a tickle." He pointed up to the sky. "We didn't see any mature stars because they're gone. They," he gestured to the soldiers "weren't kidding about the sun dissolving. It went into a state of pre-existence. Skipped nebula formulation due to mass quantum disintegration." He walked around the lab, hands dug in his pockets. "But that doesn't explain the Joam bugs. I detected Hawking radiation on them, but I doubt at this point there is any Hawking radiation because any black holes would have been gone long ago--" he stopped, realization creeping over him. "It must have been from the TARDIS. She vents Hawking radiation." 

Pasha looked like she was about to rip out his throat. "So not only are you telling me our sun dissolved because it was supposed to, your spaceship made the giant killer bugs."

"Yeah." He gave her a single nod, thoroughly chastized. It wasn't the first time he'd inadvertently brought harm to somewhere he landed, but that didn't stop the guilt from weighing on him. "In our universe, Hawking radiation doesn't have that effect. The energy must have triggered their growth spurt. I'm sorry. I'm so sorry."

"Sorry means nothing. We're all fading away here, and you bring us attack bugs?!" 

Ryan stepped in. "Look, we didn't mean it, we just crash-landed here." 

Pasha gave him a look that told him to be silent. "There's a whole planet dying. Don't you know what that's like?!"

"Yeah, I do." The Doctor's voice hardened. "Countless planets, razed to the ground. By enemy attacks. By their ruling elites, strip mining them bare. By war. You lot, you're dressed for war, but how many have you seen? My own people, starting a battle that stretched across the universe, resurrecting the dead to fight over and over again. Billions dead, across millions of planets. Do I know what's it's like to watch a planet die? To watch my friends maimed, shot, and mutilated? I know it like I know the back of my hand."

Silence hung heavy in the room. Graham felt like he'd almost intruded on something private, this Doctor was giving away all of his counterpart's secrets. The Doctor, the one they knew, steadfastly avoided speaking of her past, and now they had an inkling of why.   
The Doctor took a few deep breaths to calm himself. He'd forgotten how close this incarnation was to the Carnage of the Time War. Staring down Pasha, he said, "You could have shot us several times over, but you haven't, and I don't think you want to."

"Don't be so sure about that." she put her hand on her holstered gun.

"You've been killing people for months? Years? Look where it's gotten you. Alone, stripped down to nothing, with no hope. Let me get what I need to repair the TARDIS, and we'll be on our way. There's been enough bloodshed for one day. "

Pasha stared into him, her hand not leaving her gun. She seemed to be searching for a reason to disagree with him, to shoot him, but after a long moment, she threw up her hands. "All right, Doctor. But go as fast as you can." 

—

For the next hour, the Doctor worked frantically at the workbench, a variety of gadgets and tools in front of him, shooing off any attempts to help. He'd found a sealant glue to repair his environmental suit leg, and was now working on some sort of gadget. The humans sat and watched, uneasily glancing at Norven, who sat a short but respectful distance away. None of them expected the soldiers to go back on their agreement, but her presence still made them uneasy.

"Is he always like this?" Norven jerked his head towards the Doctor at an inopportune time. He was licking a piece of metal, his eyes widening before jamming it into a solenoid. 

"Yeah." Ryan nodded gingerly. "But we're not used to seeing him with this body."

"If he keeps changing, how do you know who he is?"

Ryan shrugged. That was the question all of them had been trying to answer.

"Still been trying to reach the Captain." Pasha joined them. "Tried the backup comms, tried the phones. No answer."

"Just like him." Norven gave a look of disgust. 

The Doctor came over, holding an awkward looking contraption the size of a cricket bat. Metal rods jutted out at random angles. 

"All right, here's the plan. The TARDIS needs a source of energy to get up and move, at least until we get her back to our universe and recharge. This, this is a small nuclear reactor. I can patch this into the main engines. I start this up, and it generates a ton of power, providing a jumpstart to the TARDIS. But I need a fuel source."

"We don't have anything radioactive here," Pasha said.

"Oh, but you do. Or you will," The Doctor said. "Ryan, remember the lab we saw when we first arrived?"

"The Zone B lab?" Pasha asked. The Doctor nodded.

"The radioactive oxygen," Ryan snapped his fingers. "But it was mostly depleted."

"Not anymore. If I reverse-well, forward-the polarity of the neutron flow, I can restore the radioactivity. The half-life of oxygen-15 is two minutes. In an hour, I'll have enough to generate the reaction I need. There are empty canisters in the back. I'm going to grab one and fill it with the oxygen-15."

"I'm coming with you," Yaz said.

"No, no, no. You are all staying here. If this goes wrong, you're exposed to radiation." His eyes darkened again. "Not losing anyone else today."

"You can't go alone, Doctor," Pasha said. "You need backup."

He regarded her unflinching gaze. With reluctance, he said, "All right. Norven, stay here with my friends." Setting the reactor down, he went to the workbench and grabbed a handful of silver shiny batons. "Electrospears. Found them when I was working on the reactor. Press the button on the underside, and they create an electric current, designed to stun. Modified to provide enough of a charge to take out the Joam bugs. " He handed one each to Pasha and Norven, keeping one from himself. 

Yaz gave a reluctant nod of assent. She hated that he'd accept Pasha's help rather than hers, but she told herself it meant she was valued. The action reminded her the most of her Doctor, always trying to protect them. 

The Doctor grabbed a spear for himself, tucking the canister under his other arm. "When it's finished, I"ll come back here. Don't worry. I'll see you soon."

After the door clanged shut, the humans and Norven looked at each other in uncomfortable silence. After a moment, the remaining soldier said. "It's about mealtime. " He ducked into a small alcove and returned with a carafe of a steaming beverage and a package in brown paper. He unfolded the paper to reveal long, pale brown blocks. "Cha-ren and protein biscuits. Want any?" 

Graham hesitated. His stomach was growling, his sandwich having been consumed hours earlier in the basement, but a few hours ago, this man had been trying to capture them. "How do we know it's not poisoned?"

"I'll go first." He poured the cha-ren into a cup. Steam rose from the cup as he drank. He paused to dip one of the protein rations into the cup. "They're too hard to eat by themselves."

Graham agreed to try some with Ryan and Yaz following his lead. He wasn't completely sure he trusted Norven, but of the two soldiers, he seemed more amiable. He hoped the Doctor had put the fear of God into him with that speech. The cha-ren was similar enough to tea, though it had more of a kick. The protein biscuits weren't half bad, especially after all these hours of being on the base. He was on his second one when he remembered the soldiers were low on rations. Setting the biscuit on the plate guiltily, he wondered if the TARDIS could drop off some food once it was fixed.

"So, what do you lot do?" Norven asked, fingers circled his cup. "Looks like the Doctor runs the show."

"We're along for the ride," Graham said. "The Doc takes us places around the universe, shows us different planets. It's mind-blowing. Can hardly believe it most days" There was a time, a few years ago, newly retired and hooked up to an IV full of poison, he'd thought his best days were behind him. 

"We're from a planet called Earth." Ryan added. "Not much different from this one, except we still have our sun."

Ryan and Graham shared some of their adventures of traveling with the Doctor and stories of Earth with Norven. Yaz didn't say much. She was thinking about the term the Doctor used-Time Lord. Was it a title he made up, or something she'd been obscuring? And what of the war he’d mentioned, that his people fought? The Doctor had always despised violence, she couldn’t picture him in a war. She had so many more questions she wanted to ask him, and she hoped she’d have the chance. This one didn’t seem as closed off as their Doctor. She glanced at the lab door. There’d been no signs of more bugs yet. This was a rare moment to relax, but she'd be able to fully let down her guard once they were aboard the TARDIS again. 

When they were in the middle of telling him about Desolation, a chime beeped from a nearby console. Norven raised his eyebrows. "It's the phone. I'll be right back."

He picked up a receiver. "Hello? Captain," he straightened up as if he commanding officer could see him. "Where have you been? Are you... Yes. Yes. They're here. Want me to...Yes. Yes." 

He hung up, turning to the humans. "Captain wants to see us right away. Me, Pasha, and the Doctor. Likely just a routine report." he added, but his expression was laced with doubt. "You can wait here."

"No, we should come with," Yaz said. 

"Captain's orders were clear. Wait here," Norven repeated.

Graham was all too willing to listen. The door to the lab looked nice and thick, and he'd much rather not face one of those Joam bugs again. On the other hand, if Norven left, they'd be defenseless.

"You'll be fine." Norven caught Graham's concerned look. "There are extra electrospears, just in case. Here." He picked one up. 

"You push this button on the other side, and it creates an electrical arc."

"Simple enough," Yaz took the spear. 

"I'll report back to you on the phone if I can," Norven said. "Otherwise, I'll meet you back here."

—  
Pasha watched as the Doctor fidgeted with what seemed like every single object in the Zone B lab. The trip here had been uneventful except for a single Joam bug, which the electrospear had easily taken out. The door was thin, and she kept on guard, waiting for others. The Doctor had already waved his small whizzy tool at the oxygen tank. Now he moved from bench to bench, picking up everything, examining, occasionally sniffing them. Was this man thorough, or was he simply insane? It must be the effect of being so many men in such a short time.

The Doctor peered into the tank. "Just about finished. Fascinating stuff in here." In all the years he'd lived, he'd never been somewhere time ran backward. And despite what it was doing to his body, he was enjoying every moment of it.

Pasha jumped at a knock at the door, before remembering bugs didn't knock. Norven stepped in. "What are you doing here?" She snapped. "You're supposed to be guarding the Doctor's friends."

"Got contacted by Trawker. From the phone in the main lab," he said.

"Where's he been?! We're getting invaded and attacked and he's hiding in his fort."

"He wants to see the Doctor," he said. "And us. Wants a full report on the base damage, the Joams, everything."

"Suppose that's the least I can do." The Doctor attached his canister to the tank, making a tight seal. With the press of a few buttons, the radioactive oxygen was sucked into the canister. He sealed it shut with a pop of the lid. It shouldn't take too much longer. The crawling on his skin was tolerable, which meant he had some time before he changed again. Grabbing the canister, he exclaimed, " _Allons-y_!"

Following Pasha and Norven through the corridors, he asked, "What's he like, this captain?"

"Mostly keeps to himself. Got top marks in the academy." He noted the disdain in Pasha's tone.

"But not top marks with you?"

"He doesn't like to get his hands dirty," she said.

"Ahhh, I know the type," The Doctor said. The High Council came to mind. He could deal with this captain. Although the crawling and discomfort weren't bad, he was itching to be on his way. A quick meeting, swing by to pick up the gang, and off they went. 

"He spends all his time in the command center, up here," Pasha indicated another large, heavy door in front of them. She keyed in a passcode, and the door wooshed open. 

Inside, they were surrounded on three sides by banks of monitors and broadcasting equipment. But the captain wasn't in sight. The Doctor peered around. "Impressive setup. All for one person?"

"He watches the whole base, keeps an eye on things," Pasha remarked. "Funny thought he'd be here..." her next words were never known because, with a shot to the back of the head, she slumped to the floor.

Norven turned around, only to be shot on the side. The Doctor tried to duck, but the laser blast grazed the side of his ear.

"Almost got you." Trawker gloated. He'd been standing to the right of the door when they came in. "But that should be enough, shouldn't it, Doctor?"

"What the..." he wanted to ask why Trawker shot his people, why he'd been shot himself, but the skin crawling intensified. Right, he'd been injured. He clenched his jaw as he dropped to the floor on his knees, bracing himself for the inevitable transformation.

"Now this is a sight! Even more amazing in person!" Trawker crooned over his screams. But his face fell when he saw the end result.   
The Doctor held out his hands. Same ones? He thought so. "Oh, right." Yes, same voice. "Funny story. Shot by a Dalek, liked this face, decided to keep it. One body for the price of two." He grinned. 

Trawker's grim expression didn't change. Without a word, he fired at the Doctor's head. He fell back, unconscious. Cautiously, he put his hand over the man's chest. Heart still beating, and fast. He was hard to kill-the laser blast should have done the job. No matter. As long as he was knocked out for a bit, Trawker could do what he needed to do. Stepping back, he pointed the gun, in case he awoke. A few moments later, his body was enveloped in violet again, and this time it changed-to a dark-haired man with large ears. 

The Doctor didn't stir. Trawker took this as his opportunity. Moving quickly, he unzipped the Doctor's environmental suit, awkwardly pulling it off. After suiting up, he grabbed the oxygen canister and patted around the suit pockets until he found the sonic screwdriver. Just before leaving, he entered the panic code on one of the consoles, the code to seal the command center shut. Nothing or no one was getting out of here, except for him. He dashed out the door just before the time delay hit zero.

\--  
Yaz paced around the lab. It felt like ages since Norven left, and there was no word from the Doctor. She stared at the phone, willing it to ring.

"They'll be fine, Yaz," Graham assured her. 

"I know," she replied, a little too snippy. Every moment of delay was ratcheting up her nerves.

Ryan's worried expression matched her own. "The electrospears-he never said how often they could be used. What if he got overrun?"

"Don't think like that, Ryan." Graham tried to put on a smile, but it faltered. "The Doc's always gotten us out of jams. What's to stop him now?"

"He had all those different bodies because they all died," Ryan pointed out. "Must have gotten caught by something. Many times."

"You're not helping." The men exchanged looks. 

There was a scrape and a shuffle outside. Yaz gripped the electrospear, just in case she needed to fight. But there was no banging, just a single push open. Before them stood the familiar orange environmental suit, worn by a man roughly half the size of Norven, with a head full of unruly brown curls.

"Hello, gang." Trawker hid his contempt behind his best grin. "I'm the Doctor."

**Notes for the Chapter:**

> I made up a hell of a lot of BS in this chapter, but I did at least try to have a basis in reality. If the BS is consistent within the story, I'm on par with a typical Doctor Who episode. Repeat to yourself: it's just a fic, I should really just relax :)


	6. Chapter 6

**Summary for the Chapter:**

> Recap: The Tenth Doctor determines in the pocket universe they’ve stumbled into, time runs backwards, which explains his de-aging, the sun disappearing, etc. He’s rigged up a small nuclear reactor. He and Pasha, the soldiers’ leader, have left the fam behind to collect Oxygen-15 to power it. While they’re doing so, he, Pasha and Norven are summoned by Captain Trawker. Inside his command center, Trawker fatally shoots Pasha and Norven and knocks the Doctor unconscious. The injury causes Ten to revert to Nine. Trawker steals his environmental suit, the Oxygen-15 canister, and the sonic, and locks the Doctor inside. At the lab, Trawker passes himself off to the fam as the Doctor.

Trawker's plan was simple. 

Listen and watch as the Doctor's explained how to repair his spaceship over the cameras. Impersonate the Doctor, take his ship, escape this planet. He never should have been left here, not with the common scum. This was his chance to rectify matters. Defiance in the face of abandonment. 

The humans, the Doctor's friends, were a complication. But he needed to go to the lab to get the reactor for the ship. He wouldn't be able to build one himself-even his vast intelligence had limits. The humans were nothing he couldn't handle. They were bright and dumb and eager and ready to follow the Doctor's every move. He could command them as easily as he commanded his platoon, simply with a softer touch. When the time came, when they'd arrived at the TARDIS, the twin laser guns holstered inside the environmental suit would be more than sufficient to take care of them. Better yet, sacrifice them to the Joams if they ran into any. He was armed to the teeth. Grenades in his trousers. Knives sheathed in his uniform shirt. Nothing was standing between him and freedom.

Trawker looked over the surprised humans, giving them a moment to take him in.  
He noticed a trace of disbelief in their manner, a slight scowl from the young man-Ryan-he reminded himself-arms akimbo on the woman. He needed to win them over, just as the Doctor had. As all of the Doctors had. " Ryan, Graham, Yaz, it's me. I've got the oxygen-15 canister right here, and we are ready to go. Hope I didn't keep you waiting too long." He added a goofy smile, trying to endear them.

"You changed again." Yaz didn't move. She studied him up and down, performing a careful inspection. "What happened?"

"Had an accidental radiation exposure when I was preparing the oxygen-15. Enough to cause a radiation burn, triggering another change. Good thing you didn't come with."

"Was Pasha exposed? Is she okay?"

"She's fine," Trawker said, feeling a sliver of remorse for the corpse he'd left in the command base. He shoved it away. 

"Where's Norven?" asked Graham. "He said he was coming back."

"No need to. Captain wanted to talk to them further." He tried to copy the quick speech of the last two Doctors. "Captain and I, we had a nice talk, straightened out everything. But he wants us to leave at once." He reached for the reactor. He needed to get them off the base before they started getting suspicious. "Ryan and Graham, carry this. Everyone ready?"

Ryan and Graham moved to pick up the reactor, but Yaz kept watching the Doctor. This one was smaller, less imposing than his three predecessors. He had all the grandiosity she'd come to expect, but his eyes lacked their usual warmth. She felt herself holding back, unwilling to follow him. She thought of her disbelief when he'd first changed and his dejection at their distance from them. She glanced at Ryan and Graham, who regarded the Doctor with reserved acceptance. 

What was the worst that could happen, she thought? She wouldn't be able to get off this planet without him. Besides, none of the Doctors they'd met had been dangerous-well, not dangerous to them, specifically. 

"Yaz, are you coming?" the Doctor asked. The lab door was open, and he stood at the threshold, waiting impatiently. He smiled at her, and it felt like a chill through her soul. There was something she couldn't place in that smile that felt almost sinister. But Ryan and Graham were looking at her expectantly, and she didn't know how to explain her reluctance.

"Sure, just want to get something." She ran to the workbench and grabbed one of the spare electrospears. "We need all the defense we can get against the Joams."

"Very good," the Doctor said but the slight dismay in her expression at her grabbing a weapon did not go unnoticed. She tried to assure herself it would be fine but found herself unable to shake off her discomfort.

\--  
In the command center, pain throbbed at the Doctor's temples, a steady pulse of agony. He opened his eyes to a grey blur, then blinked to refocus. A tiled metal ceiling several meters in front of him. What was a ceiling doing there? That's not where it belonged. 

Right. He was laying on the floor. It came back to him; he'd been shot. By the Captain. Incredibly rude, shooting him in greeting. He noticed the crawling on his skin was no more than a low hum. Had he changed again?

"Only one way to find out," he spoke aloud. A Northern accent, confirming his suspicions. Straining with effort, he slowly pushed himself upright, propping himself by leaning back on his arms. He was still in the command center. The bodies of Pasha and Norven were strewn out ahead of him. Twisting his head around there, was no sign of Trawker. He tried to stand up, but his legs refused to obey him, and he slumped to the floor. The de-aging sickness was getting exponentially worse. Not only that, but Trawker had also changed him into some kind of short trousers that only came to his knees. 

No. These were his trousers. Her trousers. The ones he'd been wearing when he came in. Trawker had taken his environmental suit. Alarm bells rang through his mind. What else had he taken? 

He patted his pockets. No sonic screwdriver. The reactor was gone too. The psychic paper was still there, not that it would do him any good. 

His head was still swimming from the change, but the realization came through like a ship in a fog: Trawker was going to try stealing the TARDIS. He'd never get past the front door, let alone take off. But Trawker didn't seem like the sort of man that would let a few details get in his way. Or a few bodies, judging by the corpses on the floor. His friends were in danger. There was no time to waste. He tried standing up, only to collapse to the floor again. 

Right. Another strategy. He crawled to the front door, pushing himself with his arms, the lower half of his body dead weight. His upper arms burned with pain by the time he got to the front door. Pressing the buttons on the left side, the access light turned red. He tried again without further success.   
That wanker had locked him in here. What did he do now? He reached into his pocket for the sonic screwdriver. Blast, he'd forgotten Trawker had it! 

He looked back at the console. It seemed light-years away. And even if he could get there, find a way to override the code, it would take him an eternity to catch up with Trawker. He couldn't tell how long he'd been out. The backwardness of this universe interfered with his ability to tell how much time had passed. There was very little chance of stopping him. 

But he had to take it. No matter what happened, he had to stop Trawker from harming his friends. 

He began the agonizing half crawl back to the control panel. With a loud grunt, he hoisted himself up onto a chair, hoping his legs would get some function back soon. He rested his hands head in his hands for a moment, willing his brain to calm, to work, to focus. Typing a few commands, he reviewed the display. The TARDIS had translated everything into a language he could use, but his brain was still reeling, trying to make sense of it. There had to be an override for the doors somewhere. He checked other options, trying to work through the murk of his mind. 

There it was! Mass evacuation used to open all the doors in this sector. The downside was fewer barriers between him and any remaining Joams. But he couldn't think of another solution, and he was running out of time. In his current state, he was defenseless against the Joams. His best defense, besides running, was running his mouth and keeping the enemy distracted, which he doubted would work on giant space cockroaches. He looked around the command center, using a rolling chair to propel himself around. He found grenades, four globes the size of an orange, stashing them in his pocket. One should have enough kaboom to take out a wall. He'd use them as a last resort. As the door whooshed open, he rolled out of the command center. He'd regained a shred of control in his legs, and could move, in tiny bits, down the corridor. Finally, something was working out.

Until one of the wheels broke, sending the offending wheel went flying off towards the wall and stopping the chair with a squeal of metal against the floor.

Letting out a string of Gallifreyan curse words, the Doctor pushed himself off the chair. He could stand, at least, though his legs were weak and shaky. If he stood long enough without moving, he would recover quickly. But long enough was not an option. He forged ahead, putting a hand to the wall for support, and occasionally stumbling. 

\--  
Yaz kept a close eye on the Doctor as they headed towards the base entrance. His speech was clipped, almost cross. A single-minded arrow to their departure, he had not stopped once to investigate anything. She told herself he was in a hurry to get off the base, per the Captain's instructions, but since when did the Doctor listen to authority figures about anything? 

"Does something seem off about the Doctor to you?" She whispered to Ryan.

"No more so than usual," he replied in a low voice, grunting a bit as he carried the reactor. Despite its size, the reactor was quite heavy. "They've all got their own personalities. Why should this one be any different?"

"I don't know, but this one gives me the creeps." Yaz kept one eye on him, not to attract his attention.

"Think you've been shaken up a little," Graham said. "With the big bugs and the soldiers being killed and all that. We're almost done here. We'll be safe soon." He gave her a reassuring smile.

Yaz tried to smile back, but it faltered. 

At the entrance to the base, the Doctor commanded the humans to quickly put on their helmets. He looked impatient, but in a way that suggested they were an inconvenience, rather than his eagerly awaiting the next adventure.

Yaz held her helmet, feeling the smooth surface in her hands. She didn't know if she trusted this Doctor with her life. She had to remind herself she hadn't trusted her Doctor at first either, but she couldn't bring herself to put on the helmet. In her brief career as a cop, the most important thing she learned (besides not pissing off her precinct captain) was to trust her gut. And her gut was headed in the opposite direction of this man. 

"Yaz, helmet on." The Doctor's tone was sharp. "We need to get out there, and soon. We don't know when the Joams will be back." 

"I know. I just worry. What if your nuclear reactor doesn't work? Then what do we do?"

The Doctor gave her another smile, flashing enough teeth to look predatory. "Don't worry about a thing. When we get to the TARDIS, I'll have it up and running in no time."

Yaz let the words wash over her for a moment. In a low voice, she said to Ryan and Graham. "The Doctor never calls the TARDIS 'it'."

"You're right," Graham said. He flashed back to what she'd told him before: _Don't call her a thing, Graham_. 

"So?" Ryan said. "Maybe he just slipped. Or this Doctor does call the TARDIS 'it'." He'd already clipped on his helmet.

"It's not just that. There's something about him that's almost...malicious" She moved closer to them." "He was so abrupt about the Captain and Pasha and Norven. He's barely spoken of them, and the Doctor likes to talk about everyone."

"Our Doctor doesn't." Graham pointed out. "There's a lot of questions she won't answer."

Although she had to admit that was true, Yaz was undeterred. "What if this is some kind of evil incarnation of the Doctor? Or because he changed so much in a short amount of time, he turned evil?"

Ryan looked doubtful, but Graham's expression softened. "Then what do we do? We can't get off this planet without the Doc." 

Just then, the Doctor strode over, shaking his head. "We should have left already. What are you all standing here for?"

Yaz caught Graham's eye as she spoke. "Well, Doctor, we were just talking, and um, you've changed. I know. You've changed a lot. And we noticed when you change, your brain gets scrambled and you forget things. So maybe we should wait here a few minutes and make sure you're okay, to fly the TARDIS and all that." She didn't know what waiting would accomplish, but it would give her time to stall and think of something else. Graham, getting the gist of what she was trying to do, nodded in agreement. 

The Doctor, however, did not agree. "What nonsense is this? I'm perfectly fine to fly the TARDIS." he scoffed, chin in the air.

"Maybe we should ask you some questions. Sometimes you forget things." Graham used his best congenial tone. He'd had years of practice with drunks on late night routes. "Like how big is the TARDIS?"

"I don't remember the exact length." the Doctor answered. "I'm sure it's in the specs."

He and Yaz exchanged a look. They didn't think the TARDIS even had specs. "How many seats in the console room?" They'd asked her about seats once, and she'd waved them off saying she had no control over the configuration. 

"It's adjustable," he replied, but he looked flustered. A bead of sweat ran down his forehead.

"Are you even the Doctor?" Yaz stepped forward, emboldened. Something was not right with this man.

"Of course I am!" he cried. "I know all of you, I know the TARDIS. Look, I've got the sonic!" He whipped it out, making it buzz.

"Do you remember anything about us?" Graham said. He thought of what the previous Doctor had known about him, the older one (he certainly would not think of, let alone refer to, Eyebrows as old). "Seems like you're not yourself, Doctor." 

"Does it matter?" the Doctor's face reddened with anger. "You're just along for the ride! Get your helmet on or I"m leaving you here!"

The Doctor-the Doctor she knew-did not say things like that. Yaz stood firm, crossing her arms. "We went to visit my grandmother. What's her name?"

"We don't have time for this trivia! What's the point? She's not important."

"My grandmother's name, Doctor." Yaz dripped the last word in venom. "What is it?" 

"Her name is Umbreen." A voice shouted from down the hall. 

Everyone turned around to look. A dark-haired man, in a grey coat and navy striped top, was staggering towards them, leaning against the wall as if he were drunk. "Her name is Umbreen. We went to her wedding, August 18th, 1947, the first woman married in Pakistan." Despite his considerable anguish, he grinned at them as he approached. 

"Doctor." Yaz felt awash in a mix of relief and vindication. This was the real Doctor. But who was this? "What happened?"

"Him." he glared at the ersatz Doctor. "Trawker, don't even think about taking my ship. She wouldn't even let you in the door, much less fly her!"

The humans whipped back to face him. "The captain?" Graham said. "But...why?"

For a moment, Trawler looked as though he would deny everything. But then he exploded in a ball of rage. "Because I didn't want to be abandoned. Again!" His lips curled in a snarl. "I found the scientists' notes. There is no alternative energy source! They knew it! But rather than telling us, they left in search of another habitable planet, like a bunch of cowards. They left us all here to die! I don't deserve that!"

"No, you don't." Within arm's length now, the Doctor teetered forward, like a baby learning to walk. Ryan put out an arm to support him. A moment of sympathy passed through his face before his features hardened. "But no more than your command deserved to be murdered." 

Ignoring the humans' shock, Trawker drew himself up, coming head to head with the Doctor. "They would have only interfered. Besides, they weren't important."

"That's where you're wrong, Trawker," The Doctor said. "They were important. So are my friends. So is Yaz's noni. Everyone is important."

"Good to know," Trawker's lips curled in an evil smile as he reached out and grabbed Yaz. Pulling out a laser gun, he held it to her head. "You're going to take me to your ship and the planet of my choice, or she gets it. Something with a tropical atmosphere, I think. I heard your friends talking, seems like you have your choice of destinations, don't you?"

Yaz stood calm, but there was a tremble in her voice. "Don't do it, Doctor! Don't let this psycho anywhere near the TARDIS!"

The Doctor froze for a moment. An impossible choice. If he made the wrong move, Yaz died. If he tried putting himself in harm's way, Trawker would blast him again, and he'd be out of commission for even longer. But a plan sparked in the back of his mind, and he tried not to smile. He just had to get the man talking. 

"Give it up, Doctor. I've won." Trawker gloated. " I've got the reactor and the oxygen canister, and I'm heavily armed. You've got no weapons, no tools, no help, you can't even stand up on your own. What are you going to do?"

'Get away from that Joam bug coming for us!" He let his eyes widen in fright as he took a step back. 

"What?! Where?!" Keeping his grip on Yaz, Trawker turned around, only to see an empty space. As he did, the Doctor reached for the back of his neck, putting him in a hold. With a chop to the back, Trakwer let go of Yaz as he fell to the floor in an unconscious heap.

"Vensusian aikido saves the day again," The Doctor stood over Trawker. "Did you lot really think he was me?"

Ryan shook his head. "Trawker didn't have me fooled for a minute."

Yaz gave him a playful slap. "Oi! You were following right after him!"

"I was just goin' along with it," Ryan protested. 

"Good to have you back, Doc." Graham smiled. "Are you able to walk?"

"Getting better." The Doctor grinned again. "Let's get my suit off this wanker and out of here before he wakes up." 

\--  
It was a relief to be back in the TARDIS again, the Doctor thought, in more ways than one. The skin crawling stopped the moment he walked in. The TARDIS must be acting as an interrupt to the backward of this universe. Aboard the TARDIS, time still moved forwards. In a way, he hated to leave this behind. It was among the more incredible phenomena he'd witnessed. The four of them would be the only ones who had traveled to a place where time ran backward, and in a few decades, no one else would even have the chance.

After checking the fittings and connections for the reactor one last time, he walked up to the console room. He'd been a little slower than usual on the walk back from the base, but now he was in as good shape as he'd ever been.

The overhead lights gave a single flash in greeting as he entered the console room. His friends were sitting on the console room stairs, chatting with each other. They'd taken off the environmental suits and helmets when they'd come aboard, but the Doctor had kept his on, a suitable cover for rainbows and braces. He didn't feel like himself in that. He had the dark jumpers and the leather jacket stashed away in his personal wardrobe, but it remained to be seen if he'd be needing them again. 

He addressed his friends. "Patched in the reactor. Oxygen-15 is loaded. Let's give it a go."

"Are you sure it's going to work?" Ryan said.

"Not completely sure of anything," he said. "Where's the fun in that?" But there was another question, he could tell by their lingering stares.

"If we get back to our universe, are you still going to be...you?" asked Yaz.

He shrugged. "I don't know. There's a possibility through symmetric temporal instability I'll change back to her, but I might be stuck like this. I'll get back to her eventually. The long way around. For once I'll know who's coming. But again, not as much fun that way." He hesitated before he ventured the next question. "Is that all right?"

"Of course we will," Yaz said quickly, and Ryan nodded in agreement. But he could see the doubt in their expressions.

Graham, unable to meet the Doctor's eyes, was more forthcoming. "I miss her. Never thought I'd say that."

A lump formed in the Doctor's throat. So typical of humans. It was hard for them to see past the physical. Some of his companions left when he changed. Most of them stayed, but he found his relationships with them transformed as much as his body. 

He surveyed again, one more time, and managed to get out: "No matter what happens, you were all fantastic." He bit his lip, thinking of the last time he'd said those words, or something like them, so many years ago. Without further ceremony, he pulled the console lever.

The console room lit up as the engines came to life. The Doctor felt their hum, every piece of machinery performing its assigned task, working in harmony. It was working. Elation filled him like a helium balloon. The console readings were still displaying gibberish, but he could work it out, reverse engineer it to where he needed to go. Just a few more buttons and…

With a sudden jerk, everyone was knocked to the floor. The lights flashed as the cloister bell rang overhead, filling the air with ominous rings. The ship rocked again, and the humans looked for something to grab, a pillar, or a stair riser. Then a yellow light filled the console room blindingly bright. Ryan closed his eyes and looked away, despite the light being followed by a prolonged, ear-splitting scream. _The Doctor._ Whatever was happening to him sounded far worse than what he'd experienced with the de-aging. Had the trip back to their universe been too much? 

Then, as suddenly as the screaming began, it stopped, a deafening silence filling the air. Smoke rose from the console again, but only on a few select panels. He looked over to Graham and Yaz, who were dusting themselves off, apparently unharmed. But where was the Doctor?

They all gathered around to the other side of the console. Relief flooded them as they saw the blonde woman they knew lying on the floor. Her hair was tousled in every direction and her face smudged with soot, but she was smiling. 

"Fam!" she cried.

"Doctor! You're back!" Ryan was elated. 

Graham reached out to pull her up. She took his hand, only to be pulled up into a hug, joined by Ryan and Yaz. She stiffened only for a moment before hugging them back. 

"Are you all right?" asked Graham. You look like a mess."

"Oi! You try aging 2000 years in five minutes and see how you look." Stepping back, she looked at the displays. "It worked. We're back in our universe. But we're almost out of power." She ran her hands over the console, delight sparkling in her eyes. "But we have just enough to go for a refill."

\--  
The Doctor parked the TARDIS in the center of 2019 Cardiff, and explained to her friends about the rift in space-time that provided a source of fuel. "It'll take a few hours. If you want to do some sightseeing, or go for tea, you won't be missing anything here." Unzipping her environmental suit, she tossed it on the steps. "Go on then. Won't leave without ya."

Graham perked up and started for the door, but Yaz touched his arm, stopping him. She searched the Doctor's face as if looking for signs of her former selves' scars. "Doctor, the other yous. You mentioned some things about your past."

"Yep. Past mes, like to flap their gums." Her smile remained bright, but her eyes looked haunted. "Nothing you need to worry about. Forget what they said."

"I can't." There was a sharp edge to Yaz's tone. She'd been so close to understanding the Doctor better, only to be pushed back. "We're your friends, Doctor."

The Time Lord's shoulders sagged. She looked down at the console, absent-mindedly fiddling with a knob. "The things they said...it happened a long time ago." She'd tried so hard to protect her friends, spare them her baggage, the blood on her hands, only to be done by her blabbermouth predecessors. She remained frozen in place like a deer in headlights. If she was still enough, they'd move on.

But Yaz wasn't moving. She could see the creases in the Doctor's forehead, her tension manifest. She wanted to ask her about everything. The Time Lords, the war, whoever Bill was. But before she could say anything else, Graham tapped her on the shoulder. 

"It's been a long day, Yaz. Nearly got killed a bunch of times. We should eat," he said.

She shot him a glare-could he stop thinking about food for five minutes?!-but he continued, "New body, new start, right Doc?" The blonde gave him a tentative nod. "The way I see it, the Doc's given all of us a new start. Let's return the favor, at least for now." 

Despite her frustration with the Doctor, she had to agree with that. She thought of where they'd been, not in the universe, but in life. Ryan, abandoned by his father. Herself, the runaway misfit. Graham beating the odds for life and love even before he faced his first alien. And how they'd all come together to be loved and accepted, no matter who they were. 

"Okay," she said. "But Doctor, if you ever want to talk about it, I'm here."

"Same goes for me," Ryan added

"That's right," Graham chimed in. "There's no better listener than a bus driver." 

Ryan rolled his eyes. "He always says that." 

"Thank you so much, fam, I will. But I'll be okay, promise," the Doctor said. "Why don't you go to tea? The TARDIS should be fueled up by the time you get back, and then I can take you home."

The Doctor leaned against the console, watching as the humans filed out. She breathed a sigh of relief as the door closed. Yaz had been unusually insistent this time, wanting to know about the past she'd worked so hard to protect them from. It was a good thing they were going home after this. Next time, she'd whisk them off to another amazing planet, and they'd have too good a time to ask intrusive questions. 

She smiled, turning back to the console, plotting out their next adventure. But there was one thought she couldn't get out of her head: regardless of the universe, the past had a way of catching up with her.

**Notes for the Chapter:**

> Aaaaaand that's it! Thank you, lovely readers, for sticking around this far. I hope you enjoyed.

**Author's Note:**

> Special thanks to jolivira and taka for discussion.
> 
> The information about how the TARDIS is powered is from whoniverse.net, though I made up the exhaust part. The best part of writing for this fandom is how much shit you can make up :)


End file.
